Lies Mother Told You
Untruths and half truths from that supposed
mother of all sources, the Internet
(Or more specifically, Internet user forums)

The Internet. You can look up how to replace the belt on your clothes dryer, find a tax guy, or discover answers to trivia questions. Google is everyone's friend. But user forums are a huge problem in powersports. Forums encourage folks who pretend to be experts yet who know no more about what they are talking about than does your dog; folks who don't realize that being able to impress people even more ignorant than yourself doesn't qualify you. Some posters knowingly or unknowingly prey on innocents, people looking for answers and getting instead the wrong, even harmful information. But worst of all, these Internet experts look down their noses at the genuinely qualified in the industry, mocking and dissing them publicly, all the while dispensing advice that any first-semester tech school student would laugh at. If motorcycle user forums are such good sources of wisdom, why aren't any of the real issues of maintaining a bike found there? Instead, user forums deal in the trivial, the faddish, the apocryphal, the vacuous, and do so with a rabid, almost religious devotion to extemporaneous ideas, no matter how unqualified. Aren't there wonderfully talented folks on forums? Sure. Yet these same folks who have never made a living servicing motorcycles don't know how to check their oil, and career mechanics can't tell them.

The threat of the subject demands a distinctly corrective, even purgative remedy. I am certainly not doing it for recognition. My sincere hope is that a few lost motorcycling souls, poisoned and bruised by the 'net, will find respite here.

Carburetors Engines Electrical General

Item: The supposed evils of ethanol-laced gasoline

This is the big lie right now. The AMA is doing the powersports industry a grave disservice by perpetuating the myth that oxygenated gasoline is harmful to powersports vehicles. It just isn't so. And thousands of echos all over the Internet don't make this fallacy any more real. Let's look at the hype in terms of its three claims: corrosion, loss of performance, and chemical damage of rubber components.

Kind of carburetor leprosy, huh? About as bad as it gets. Ugly. Many blame oxygenated fuel for this. That is nonsense. This wasn't caused by water in the gas; this was caused by water, period. I other words, a fuel tank rhat sat under the eave of a house or barn and accumulated rainwater. Pre-1978 carburetors, due to their high zinc content, are more prone than are later models to this kind of corrosion depending on how they are stored and cared for. But it wasn't ethanol that did this.

First, corrosion. Oxygenated gasoline does not corrode powersports carburetors. Where this idea generated is actually in the marine world, and it is in fact the National Marine Manufacturers Association (NMMA) that is fanning these flames of hysteria: lobbying the government, speaking at hearings and so forth, and this is no doubt where the AMA joined the controversy, though why they feel boats is in their domain I haven't a clue. The fact is marine engines' carburetors still have lacquered cork gaskets in many cases, bimetallic construction (steel float bowls bolted to low grade aluminum carb bodies), and other very basic technology that in fact lends itself to maintenance issues such as corrosion and deterioration. You can find this same technology on your lawn mower, by the way. But not on any motorcycle made in the last 60 years. Certainly, advanced gasoline formulas and the eventual presence of moisture is going to wreak havok on this kind of carburetor, and I don't fault the marine industry for attempting to defend itself. I think it would better serve its customers however by bringing its fuel systems into the modern era. And since the stationary engine industry (lawn mowers, portable generators, etc.) use very similar carburetors, maybe they should be advocating alongside the NMMA. But guess what, they aren't. So motorcycle carburetors never corrode? Not saying that. But you can't blame oxygenated fuel for the mostly pre-1978 motorcycle carburetor, made of a high percentage of zinc, that corrodes internally, sometimes fiercely. But they always have, and ethanol is not appreciably hastening that. No motorcycle, ATV, scooter, personal watercraft, snowmobile, or recreational vehicle's carburetor is more at risk for corrosion than it ever was. That's just a simple fact.

Second, performance issues. Motorcycle manufacturers have to make a lot of compromises in production and nowhere is this more evident than in carburetors. Thus many vintage Japanese carbs benefit from careful, knowledgable tweaks, and have since the very beginning when new, long before ethanol. What's changed is back in the day we rightly blamed the carburetor (though in some cases popular carb tweaks actually compensate for a lack of engine maintenance), but today we blame ethanol. Do you see the idiocy of this? The current fuss over oxygenated fuel is a sacrificial lamb, an answer looking for a question, a cause in need of a sponsor. And that is all it is. Adding oxygen to carburetion does not upset it. Only in cases where the engine is not in proper tune (and in my 45 years in the service end of this industry, I can assure you ninety-five percent of the vintage bikes out there suffer from tuning shortcomings) and thus its manufacturer-designed richness margin at risk, is this evident. Properly maintained vintage powersports engines do not suffer performance wise from the use of oxygenated fuel. They just don't and anyone who stops to think about it knows it.

Third, deterioration of rubber parts. To cut to the chase, the only rubber carburetor parts affected negatively by today's fuel are those chewing gum like parts found in that bane of the industry, carb rebuild kits. No stock rubber parts and no high quality stock or aftermarket replacement parts swell or break down any more than they did before oxygenates came on the scene. So they do swell? Sure, they did in 1970 and if those OEM parts could be bought today you would see them still swell slightly. And though these parts weren't Viton in most cases, they were a high grade of rubber. Anyone who actually worked on these bikes back then knows this. Certain sellers of Viton rubber parts have vilified those who do not sell or work exclusively with Viton, and this is a shame. Lack of technical and historical understanding and more than a little naivete are behind much of this.

This whole oxygenate thing is incredibly irrational. And better than anything I can think of it represents the unreal world of the Internet, the Twilight Zone environment in which all the rules change and even gravity is reversed.

Additional reading: Gasoline,  Oxygenated gasoline,  Carb kits,  Carb McKits

Item: Carburetor rejetting

Second only to the oxygenates swirl, there is hardly more misinformation online than that regarding rejetting carburetors to suit changes to an engine. The bald but unpopular fact is, very, very few aftermarket exhausts do anything to vintage Japanese motorcycle engines. I hear from folks all the time who want to tell me all about their exhaust, but fail to mention they have modified their air filter configuation. I always have to ask; it just never seems to occur to folks that the air intake specifications affect carburetor jetting many many times more than does the exhaust.

Here are three very important things to keep in mind. First, vintage production Japanese powersports engines up to the late 1980s have so little valve overlap in their design that exhaust tuning, that is, affecting power through application of an engineered exhaust system, just isn't possible. It just isn't. Second, what these same engines do have is extremely restricted intake systems, due to sound regulations that caused manufacturers to strangle incoming air to quiet the intake. Thus, making any changes to the intake on these bikes has an enormous affect on carburetion, often to the tune of eight to ten main jet sizes. Yup, eight to ten. And the third thing to remember is, when an aftermarket exhaust does affect an engine, and thus carburetion, it is because it is very loud. That's it. And even then, the effect is not all that much, usually just one to two main jet sizes.

Terry Vance, of Vance and Hines fame, once said in an interview of his Vance and Hines exhausts, "We don't sell performance, we sell fashion." This is likely scandalous to some. But the bald truth is, the fitting of aftermarket exhausts do not necessarily result in the need for carburetor changes. Virtually all of the aftermarket exhausts for vintage bikes, and even many of those for modern bikes, are styling products, not performance products.

Additional reading: Carb rejetting,  Aftermarket exhausts,  Carburetors and altitude

Item: Carburetor throttle shaft seals

Another subject in the forum tyrant's stock in trade, the overemphasis on the felt and rubber seals and their influence on carburetor function, is especially onerous.

Many on forums insist that engine performance issues can frequently be traced to vacuum leaks at the throttle shafts. Sounds logical. Too bad it just isn't so. In more than 45 years rebuilding carburetors, I have yet to encounter this. In each case in my experience where someone believed the seals to be the cause of an unwanted performance glitch, it was found that there was another, completely different issue, at play. Whether bowl venting problems, incomplete cleaning, inadvisable use of aftermarket parts, or simply inexpert adjustment, these shortcomings are hundreds of times more often the problem than are vacuum leaks at the throttle shafts.

A used but still intact felt throttle shaft seal. These seals, only recently made available on the aftermarjet, are not the silver bullet many want them to be. They are more dust seals than anything else.

This fallacy is bolstered on forums because of another misconception, that of spraying any number of materials onto carburetors and noting whether the engine responds. This is a "hack" procedure, that is, one no professional tech would ever use. The correct test is the less air test. See my article on that test, linked below.

Many Keihin carbs, most notably Honda GL1000, have seals that are so loose you would intuit they would have to affect performance. But guess what, they don't. The fact is, the felt seals on carburetor throttle and choke shafts are not perfect seals and are not designed to be. Think about it: can felt really seal? They are dust seals for the most part. Carburetors having these seals are engineered to work properly with a small air leak. You can attempt to tighten this up if you must, but it will be fruitless. It will not solve a performance issue. Determine and solve the real problem instead.

Additional reading: Throttle shaft seals, The 60/40 rule

Item: Carburetor float levels

The idea of altering a carb's float level from OEM spec to solve a fuel leak is absurd, yet many suffer from this delusion. Float level is a function of carburetor tuning, not sealing. That is, the manufacturer determines the fuel level based on air/fuel mixture targets, not on keeping the carb from overflowing. Even a tiny change in float level makes a dramatic difference in engine performance. Thus a float level so badly misadjusted as to cause overflow would have long since resulted in so poor engine performance that it would vastly overshadow leakage concerns. The bike would barely run. Nor does a carb's float level change over time. Once set, it's set. On top of this, does it really make sense that a leak should be solved (presuming for a moment that it could be) by altering the carburetor from OEM spec? Again, it's nonsense. Where do carburetor leaks come from then? There are at least seven potential areas: the float valve of course, blocked bowl vents, cracked overflow standpipes, rusted drain screws, a bad float, bad casting o-rings, rust or water in the float bowl, and more. Talk to a mechanic about these. But don't readjust your float level.

Additional reading: Float levels,  More on float levels, Setting float level

Item: Honda's idle drop procedure

As a career powersports tech and votech educator, I find it more than curious, even humorous, that user forums propagate a technique that has so little to do with proper tuning and which owes so much to exhaust emissions goals. Honda's idle drop procedure is not part of correct idle mixture screw adjustment. It's goal is to slightly screw up the adjustment from best to a little worse than best, to accommodate emissions considerations.

I have written about this elsewhere, but note that the idle drop procedure is uniquely Honda's. It originated on their early cars, in the slightly more involved form of the propane enrichment procedure. In that procedure, the tech attached to the carburetor a bottle of propane and adjusted the idle mixture in this condition. After getting the highest and smoothest idle possible, the time-honored outcome, he then removed the propane bottle and gave the car back to the customer with no additional carburetor adjustments. What was the outcome? Of course! The idle mix was set a bit on the lean side. An emissions deal. For good or bad. When writing the same thing in their bike manuals, Honda hit on the less expensive equivalent of the idle drop procedure. Same setting, same goal, and same outcome. The mix is optimized, then intentionally worsened a certain amount, in the name of emissions. Call this whatever you like, it is not tuning.

To be fair, perhaps many motorcycle owners find the idle drop procedure to be a more accessible method of adjusting their pilot screws than either doing it the traditional way by ear or by using an exhaust gas analyzer. I can accept that. I think it a little juvenile, but I guess it works for some. What gets my back up is forums all over regurgitating the procedure as if it's best practice, or even good practice. Nonsense.

Additional reading: The Keihin idle circuit white paper

Item: Patently bad carburetor rebuilding practices

There is a ton of this out there. But let's take just five items: using wire on throttles, burnishing float valve seats, cleaning carburetors with PineSol, removing pilot screw blanking plugs incorrectly, and using pliers on float pivot pins.

First, the wire: If you look closely at the throttle plate of a modern CV carburetor you'll notice the plate's edge is not machined at 90 degrees, it is rather at an oblique angle; it is in fact a knife edge. This angle accomodates the angle that the plate is itself mounted in the carburetor, so that the edge of the throttle plate seals perfectly against the carburetor body. And, the throttle plate is either brass or even softer aluminum. Dragging ANYTHING under the exquisitely-machined surface of the throttle plate is a crime, morally if not legally. Whether wire, or a plastic tie or whatever, the throttle plate is not going to survive this nonsense without damage. The resulting groove scratched into the edge of the throttle plate will pass more air than the plate's position willl call for, throwing off everything -- synchronization, idle speed, the works.

Second, burnishing float valve seats: A couple of how-to books on the 'net instruct to use an abrasive to "clean" float valve seats. I cringe every time this comes up in conversation or I see it mentioned again on user forums. I have contacted one of the books' authors, who was responsive to suggestions, and that is good, though I don't know if the book in question was revised. I have two problems with burnishing float valve seats. One, it has the real potential of changing the shape of the carefully machined taper in the seat, and worse, even making it out-of-round. That's bad enough, as the seats in many carburetors are not replaceable and thus the carburetor body itself is ruined. Two, there is more than just potential but real danger, in another result of burnishing and that is changing the height of the seat's sealing surface relative to the carburetor casting. This is bad because many mid 80s Keihins have non-adjustable floats. So changes to the height of the float valve seat necessarily changes float height also, and it can't be compensated for. I recently had a very valuable Euro model CB1100R set in that suffered from these two issues. How long is it going to be I wonder before folks stop doing this?

Third, PineSol: The use of PineSol is mostly pretty innocuous. It is too useless to be harmful, generally speaking. It simply does not work. Now, if your carbs can be cleaned to your satisfaction in a bucket of paint thinner, then hey, go for it. That is the result you will get; that is what PineSol is, a solvent. However, most of us expect a little more. Where things get nasty is, there is actually a problem with PineSol beyond its uselessness, and that is, being an organic solvent, you can leave carbs in too long, in which case they will discolor badly and the only remedy then is abrasive blasting. Hmm. Then there's PineSol's flammabilty to consider. Being an oil, caution is warranted. No heat or open flames, as they say. Yes, that means don't even use it in an ultrasonic bath, even without the heater turned on. Just the ultrasonic waves are enough to ignite it.

Fourth, incorrectly removing pilot screw blanking caps: Aluminum caps resembling miniature manhole covers are found on all of Honda's final generation of Keihin carburetors. The caps, like the plastic and then aluminum flags before them, are designed to discourage end users from altering idle mixture settings. But the factory, as always, left room for the professional to service this part, making it easily removable. The usual way is to drill a small hole in the cap and then using a sheet metal screw, yank it out. I typically see this done incorrectly. When I remove an idle mixture screw and see a drill point on its head, I know someone fed the drill bit in until it went through the cap and started drilling into the actual screw. Not good. Many times doing this will spin the screw so hard it snaps off its tip inside the carb casting. Professionals use a drill stop on their drill to avoid this.

Fifth, using pliers on float pivot pins: Broken float pivot stantions are a fairly common finding on certain models of carburetors, when the previous mechanic has not been careful. Though obviously heavy corrosion around the part leads to its almost inevitable failure, even when there is not significant corrosion, the stantions may still snap, if the pivot pin is not removed correctly. And correctly means with a properly fitting drift, not a pair of pliers. The use of pliers puts divits on the pin that make it seize in the stantions, resulting in breakage of the stantions during installation or more commonly, during a later removal.

Additional reading: Bad practice,  Carburetor rebuilding techniques,  Carb kits

Item: Vapor honing carburetors

Actually, I am not totally against vapor honing as it's called. In fact, I do it in my shop. As I say, I believe in it. I just think many approach media blasting of any kind with much less caution than they should.

Though a relative newcomer to the field, Vapor Honing Technologies of North Carolina has already established itself as a force in the marketplace.

Vapor honing is very prevalent today. But it is also also misrepresented and misunderstood. Here are some things to consider.

First, vapor honing, or more properly, wet abrasive blasting, for all its innocuous name, still abrasive blasting, using the very same glass beads and/or aluminum oxide powder that is used in dry blasting. No one who has given most of their life to this industry can think of abrasive blasting engine oarts without giving serious pause. Abrasive media blasting has an incredibly tarnished reputation in my view. And not just mine. Though still regarded by many a historic and viable part of powersports repair and restoration, an increasing number of industry insiders are turning away from it in favor of soda blasting. The problem is abrasive particles just don't play fair. Sprayed onto engine (and increasingly, carburetor) parts, they inevitably find permanent homes in crevices and passages, and cannot be extracted, no matter the technique. This is so pervasive and so well known that soda, which dissolves in hot water and thus is much less harmful to engines and far more easily cleaned out, is rapidly taking over as the method of choice among careful and thinking practitioners, though it has its issues also.

Next, it can be argued that the water in the vapor honing method acts as a barrier to the abrasive media going deep into engine passages, by offering a higher effective viscosity that limits much of the blast's contact to just the part's surface, as well as offering a "washing" effect. I am sure this is at least partly true, and my experience seems to confirm it. I just have a hard time getting away from the fact of abrasive blasting anything, and especially parts having tiny, critical, and hard to clean oil or fuel passages. Shooting tiny non-destructive (referring to the media, not the part) abrasive particles into small, mostly blind-bored holes? Really? Okay, but the water side of the water/media ratio has to be very high, the carbs pre-cleaned and post-cleaned, and cleaned repeatedly again, and fanatic, meticulous care taken to insure no residue is left behind. And that is a big "but." To use it and stay out of trouble requires a truly obsessive ethic: Multiple washings, aerosol chasers, compressed air, over and over. Medical doctors should be so scrupulous. Seriously.

Mikuni RS racing carburetors treated in the vapor honing machine. Can't argue that vapor honing doesn't leave a nice finish. This has more or less become the standard in powersports restoration.

Lastly, I take grave exception to those who use wet blasting in the place of normal, proven carb cleaning methods. It leaves me speechless. One rebuilder in particular actually started his business just a few years ago using solely this "cleaning" method (he is on record as disdaining ultrasonic). Whatever you believe about vapor honing, and again, I have a machine -- and as I say I am not against its proper, careful use, I just view it as tightrope walking -- it is NOT a cleaning method. It is inconceivable to me that anyone could possibly regard it as such. Particularly alarming is how readily the public accepts this notion. It's completely illogical. As if waxing your car will make it run better.

Item: The aircut valve swirl

I won't say I was the first on the Internet to promote defeating Keihin carburetor aircut valves. I probably wasn't the first. But if not, darn close. I think every current user forum relating to Keihin carbs on vintage Honda bikes got the information from me. And I got it from another career tech. Then a few years ago someone finds out it was part of a factory-recommended racing mod, suggested in a race kit pamphlet. Interesting.

Whatever, the point is only that it is a time-honored (not to mention factory-sanctioned) procedure that is valid and not hack, not one of the numerous highly dubious suggestions made on user forums, and a technique many both on forums and elsewhere have benefitted from. Okay. But, I see a trend about the aircut valve defeat's discussion on the Internet I want to address.

Two things are misunderstood about the aircut valve defeat. One, it is not a tweak. That is, a performance improvement. It is not intended to solve any rideability issues. Far from it. It results on no change in performance whatsoever. The purpose of defeating the aircut valve is solely to eliminate it as a maintnance item. That's it. Those aircut valve diaphragms are expensive and need to be replaced fairly often. So, when you do a carb rebuild, to reduce cost and repeated diaphragm failure, just defeat or bypass the system. It's easy, very effective, and has no negative consequences. I explain in most of my carb books how to do the procedure.

Number two, I have noticed folks are confused and assume they must change the idle mixture (pilot) screw setting, increase it in other words, to compensate for the defeated aircut valve. Nope. Not so. Yes, these two things are connected, in that they are both part of the carburetor's idle circuit. And yes, you should slightly increase the pilot screw setting over the factory spec. But you don't increase it because of the aircut defeat. You increase the pilot screw setting for completely different reasons having to do with the state of tune of the engine. Suffice it to say that you should have increased the pilot screw setting long before ever thinking about the aircut valve.

Do the pilot screw readjust to get better starts and idling. Do the aircut defeat to eliminate it as a regular maintnance chore. Do them both. But one does not affect the other.

Additional reading: Keihin idle circuits

Item: Facing Japanese valves

Honda's 1971 technical bulletin announcing their use of plasma-coated valves. Note that both wearing surfaces, the valve's face and its tip, are coated.

A few websites persist in perpetuating the fallacy that Honda and other Japanese makers' engine's valves can be resurfaced. It's a really bad idea. And it is a perfect example of so many who regard themselves as knowing so much more than the average professional mechanic, or more than the motorcycle manufacturers for that matter. Yet, what they don't know puts them in a league below, not above, the dealer or manufacturer. Low performance thinking, I call it.

At one time most motorcycle manufacturers used quality materials in their valves, and actually made them in two pieces, the head of the valve of one material and the stem of another. They were actually welded together. In those days, you could take a magnet and detect the difference. Kawasaki's 903cc Z1 of 1973 and later was one example of this two-piece valve. However, at about this same time many Japanese manufacturers, eventually including Kawasaki, started making their valves of one piece to streamline manufacturing and reduce costs. The valve was likely made by spinning a metal rod and slamming it against a hard surface to create the mushroom that would afterward be machined to make the valve's head. The thing is, a softer material was used, and that is important.

Honda announced what they were doing in a 1971 service bulletin. Eventually however all the Japanese manufacturers started doing it this way. It's why all Japanese valves mede during this period (1970s through the 1980s) are junk, that is, they recede so quickly, in most cases quickly enough to affect cylinder compression in just 15,000 miles, and become paperweights in only 25,000. Every career mechanic has heard of "the Ninja syndrome" for example, which refers to the period in the early to mid 1980s when Kawasaki's first-generation Ninjas's valves significantly receded extremely quickly, usually before 10,000 miles, and after just a few more miles you could literally shave with them. No joke. This happens because the valves are soft and the only reason they work at all is they are plated. Actually a plasma coating called Stellite, it's only a few thousandths thick, with the valve soft underneath. You really don't want to fool with that.

These valves wear quickly, despite being plasma-coated. You want to remove that coating and see how long they will last then?

Back in the day when Japanese bike valves could be faced, this is how it was done, using a specially designed automotive-oriented machine. Not any more.

For some time now Japanese valves have been an issue, wearing out way before their time. Reconditioning these valves, either by hand or using a machine, is bad practice. It will merely make them recede that much faster.

Item: Valve jobs

Proper valve work on a cylinder head is grossly misrepresented by many. For most of my 45-plus year career in powersports I have pounded this drum, because it needs to be pounded. A professional valve job is not cleaning things up and lapping the valves into their seats. Not even close. I do cylinder heads on a regular basis and I haven't owned a valve lapping stick since Carter was president.

Cylinder head valve seats wear by widening, getting rounded edges, and out-of-round, and they pit. They even shift slightly in the combustion chamber, especially certain models. Interestingly, intake seats exhibit mostly widening and rounded edges, whereas exhaust seats are heavy on the pitting due to their more severe chemical abuse from combustion's extreme heat. Shifting happens with both intake and exhaust seats, especially in certain model vehicles. Valves and valve guides also wear, of course. Valve guides wear most on rocker arm engines, and surprisingly, the exhaust guides on these same engines wear more than the intakes.

Valve recession is a big deal. Recession looks like a groove worn into the valve's face as the valve gradually sinks into the cylinder head. The softer intakes recede more than the exhausts. Recession is the normal course of valve wear, but it can be excessive. Recession results in two bad things. One, it ruins the valve's seal. As recession progresses, the groove grows, making the valve's originally smooth sealing face compromised, with the cylinder's compression suffering commensurately. Usually this happens over a long period of time, but in some engines it takes fewer than 20,000 miles. As if this wasn't bad enough, the second downside of recession is that it moves the valve toward its lifter, whether rocker arm, actuating bucket, or whatever. Thus valve clearance goes away, affecting cylinder compression even more. This needs to be monitired in Japanese engines in particular, which are the most susceptible to valve recession. If left unchecked, recession steadily lowers compression and eventually results in burned valves. These are the reasons then for a valve job: worn seats and receded valves. And I hope you can now understand why lapping valves fixes neither.

Valve lapping is a backyard technique. Pros consider it hack, plain and simple. Although some OEMS legitimize it, is is far from legitimate. First, why would you deliberately recede your valves, hastening one of the worst things that can happen to a valve and something you should be trying to avoid? Second, a valve-to-seat interface that needs to be lapped to complete a "valve job" is one whose seal was not good enough by itself. The valve job itself is inferior from the get-go. You can't escape that fact.

A cylinder head's valve seat is pretty interesting. It has three angles minimum. The sealing surface, where the valve will reside, is a 45 degree angle (in all Japanese and most other brands, post-WWII). This is the heart of the valve seat, the holy grail. Most valve seats also have two additional angles, a 60 degree angle transitioning from port to seat, and a 30 degree angle transitioning from seat to combustion chamber. These supporting angles, which vary a few degrees with manufacturer and model, ease airflow across the valve seat, so that the physical presence of the seat in the airstream presents less of an obstruction. So critical is this transition that knowledgeable engine builders estimate that more than 80 percent of the performance benefit of any head work, including porting, is due to what happens in this exact spot. The Superflow corporation, makers of the most widely-used cylinder head gas flowing equipment in the world, has also long been on record as holding that the valve seat is the most important place in the port, flow-wise, and thus, again, the most impactive on performance. I have said for many years now that the hidden, real benefit of porting is what is done to the seat, in many cases accidentally, that is, with no knowledge of its importance. Do a good, professional valve job and you will reap at least 80 percent of what you hope to gain by porting, and probably 100 percent.

A real valve job looks like this. First the head is inspected for damage that would make spending time and resources on the valves and seats cost-prohibitive. The condition of the valves, of course. But also loose valve seats, cracked or worn valve guides, heavily damaged gasket surfaces, combustion chamber damage, problems with studs or threads, oil passage issues, etc. Once the head is deemed usable and its threads and whatnot repaired, it is ultrasonically cleaned and painted. The first valve-specific step is to machine the seat's 45 degree to square it up, improve its finish, and dress away pitting and unevenness. Then Prussian Blue is carefully smeared on the seat and the valve inserted, to "register" where on the valve's face the seat is contacting it. It's important that the contact be centered on the valve's face. If it is off, and it usually is, then the 30 and 60 degree angles are machined as necessary to move the contact where it belongs, as confirmed by repeated blue checks. If for example the valve's contact is off center toward the combustion chamber, then the 30 degree angle needs to be machined slightly. If on the other hand the contact is off center the other way, toward the valve guide, then the 60 degree angle needs to be machined a bit to move the contact toward the combustion chamber. Once each valve is centered on its seat, you're not done. Now that 45 degree needs to be either widened or narrowed, as needed, for good sealing and long life. Narrow seats seal the best, but wider ones promote the longest life. A compromise is sought between the two, and though manufacturers suggest certain specifications, it is up to the technician to decide. The 45 degree is narrowed, if needed, by machining both 30 and 60 an equal amount. It is widened by machining the 45 itself.

Beyond this basic valve job there are extra steps for preparing the head for aftermarket cams, and special tipping and sinking procedures to set up a shim type head. A 24-valve shim type Honda CBX valve job takes 20 hours or more to complete. A Gold Wing head 3 to 5 hours.

Additional reading: Valve jobs done right

Item: The valve clearance myth

Nearly everyone thinks valve clearances are determined by heat expansion. That is, that a manufacturer specifies a particular clearance to allow for the growing of the valve train parts and subsequent loss of clearance between valve stem and the rest of the valve train. This is not so. Valve clearance has nothing to do with heat expansion. Most engines actually get looser valve clearances with heat, not tighter. Let's explore this in detail.

The cam lobe profile layed out linearly, allowing a more intuitive view of the transitional nature of the clearance ramps.

A camshaft has some interestingly complex shapes. It is not just a stick with bumps on it. If you take the familiar cam lobe profile and convert it into a linear form, something interesting becomes evident. A virtually invisible aspect of the camshaft becomes very plain--clearance ramps. Clearance ramps are those two transition areas on either side of the lobe. The ramp on the opening side of the lobe takes up the lash and readies the valve for liftoff, when the valve and its parts are suddenly catapulted into movement. The ramp gradually applies tension to the valve train so that all its gaps are taken up, before the valve is popped open. This greatly extends the life of the valve. Similarly, the ramp on the closing side ensures that the valve is not closed too suddenly, but rather gradually enough to physically protect the valve and prevent valve bounce. The clearance ramps, on both the opening and closing sides of he lobe, are shock absorbers for the valve, transition points on the cam. These ramps may be the most critical parts of the camshaft. They certainly are the least understood by the average person.

When the valve is opening and closing hundreds of times a second, transition is very important. To better appreciate the cam ramps' roles, consider that ramps aren't the same shape with the different valve train types. A pushrod engine needs the most ramp on its cam. It needs a lot of transition because the pushrod design has a lot of parts flailing around that can easily get tangled up. Movement of all that inertia has to be undertaken much more carefully. A shim type valve train on the other hand needs the least amount of ramp, for the same reason. Its moving parts are minimal and very tightly controlled, and need less coddling. So the clearance ramps on pusrod engines and on rocker arm engines and on shim type engines are all very different.

The cam lobe nomenclature. The flank accelerates the valve, the nose detemines the valve's maximumum opening, the ramps transition the valve.

The lobes on a stock camshaft and on a high performance camshaft also obviously have very different shapes. The flank, that part of the cam lobe that actually opens the valve, is the most noticeable difference. The shallow flank of a mild cam opens the valve gently. The steep flank of a performance cam opens the valve more abruptly. Whether stock or high performance, there is only so much territory in the lobe with which the designer can create the wanted shape. The mild cam therefore has a lot of ramp because less flank is taking up room. The performance cam on the other hand has less ramp because more of the cam's lobe is taken up by the flank, so there is less left over for the ramp. Mild cams have lots of ramp, performance cams have less ramp. And this is why a high performance camshaft specifies a larger than stock valve clearance. It's not due to heat, remember. Where do you suppose the material for the high performance cam's extra lobe profile comes from? From the clearance ramp, of course! The high performance cam designer steals area from the clearance ramp to give it to the rest of the cam. But this reduced clearance ramp means reduced babysitting of the valve, less protection of it on opening and closing. So guess what? The valve clearance is increased to compensate, to extend, to regain some that was lost, of the reduced valve transition time. So a camshaft with a lot of ramp needs less valve clearance, and one with less ramp needs more. The two are inversely related. And the point is that they are related, very closely. This is in fact why the transitional ramps are known among engineers as clearance ramps.

And heat is not part of the picture. A hot valve actually increases its clearance, it does not decrease it. As the overhead cam engine's valve heats up, it expands more than the castings around it, resulting in the head of the valve increasing in size, the valve moving downward away from the cam, and the clearance increasing. Prove it to yourself. Check your hke's valve clearances cold then hot. There is an exception however, and that is the pushrod engine. In pushrod designs, the considerable mass and length of the pushrods and associated parts expand more than the valve, and the valve train tightens up -- clearance diminishes. Thus the valve clearances in pushrod engines do get tighter with heat, whereas the valve clearances in OHC engines do not. But the function of valve clearance in each engine is the same -- to work with the cam's clearance ramp to babysit the valve train.

Item: The lobe center myth

It's incredible to me how many think that lobe center is a timing procedure. It is not.

Aftermarket camshafts are marketed largely on the basis of their numbers: When in crankshaft degrees the valve opens, when it closes, and how long it stays open. Because of an interesting fact of cam lobe geometry, namely how utterly gradually and therefore gently cams start their valve's opening (and on the other end complete its closing), it is very innaccurate to simply monitor those points on a degree wheel. They are too slow, giving rise to error when measuring. So the cam world agreed long ago to chose an arbitrary point somewhat later, when all the gradual-ness in the cam lobe has gone past, to begin to consider the valve as opened or closed. This point is known as the "check height." Everyone involved with cams, from maker to seller to end user, utilizes a check height when working with the camshaft.

The difficulty is, whether from tradition or whatever, or just plain snarkiness, there are any number of different checking heights being used. Some manufacturers, typically automotive and/or very old school cam makers used to working with pushrod engines, use 0.050". Others, focused primarily on ultra-performance overhead cam engines deploying relatively sophisticated inverted bucket type valve trains, use a mere 0.020". Still others, including all of the Big Four Japanese marques, rely on 0.040", i.e. one millimeter. The result is that comparisons of cams measured using different check heights are virtually meaningless.

This is where lobe center comes in. The lobe center calculation (that is what it is, a calculation, not really a procedure) mathematically (not physically) finds the midpoint between opening and closing, completely eliminating the importance of the actual opening and closing points, and thus superceding the effect of check height on camshaft measurement. The center if a thing is always the center, regardless of how early or late the counting starts. What the lobe center method does is arbitrate; it acts as a sort of universal translater between the different cam manufacturers. Now their products can be compared in meaningful, useful ways.

However, somewhere along the way this useful ecumenicalization has been perverted. All of a sudden, lobe center now is being spoken of as being all about cam timing, to the truly unfortunate point that it has even displaced the importance of the intake valve's opening, and especially closing, points, the most sacred of all cam measurements. Instead, folks talk of timing with lobe center, matching cam to engine with lobe center, and I expect next we'll have the United Nations declare lobe center a human right or some such nonsense. (I don't really believe that, but with the silliness in this trend, you never know...)

Lobe center is about comparing two cams. It has nothing to do with cam timing. It has no relevance to cylinder head design. Presenting it as such is wrong, time wasting and maddingly obfuscating.

Recommended reading: Lobe center,   Camshafts,   Engine building secrets,   Horsepower,   Engine assembly,   Big bore kits,   Engine math

Item: Hot cylinder compression tests

I hear constantly from customers who, when I ask them to check cylinder compression before sending me their carburetors, tell me they can't because the bike doesn't run. Sigh.

I don't know or care where this myth started, but it's just one more example of the misinformation that characterizes Internet forums. I have been in the industry for over 46 years, half of that in votech, worked for both Honda and Kawasaki U.S. headquarters, the latter for whom I managed dealer training, have enough certificates to quite literally wallpaper a medium sized room, and I can assure you, no professional tech ever warms up an engine before doing a compression test.

Related to this, I often read on forums where a poster says he checked compression then checked it again after squirting oil in the cylinder, seemingly as if maybe that way the result would be better. This is another thing no pro mechanic ever does. Even the legitimate addition of oil to see if worn rings are contributing to low compression hasn't been accepted practice for over 50 years. That's what a leakdown test is for. And as for adding oil to sort of "hedge your bet"... Ack! Unbelievable.

Item: Abrasive-blasting clutch steel discs

I'm not sure this is done much any more, but I still occasionally see it mentioned on forums. One of the things engine builders used to do is glass bead the steel discs in Japanese engines. They meant well, but they really didn't know what they were doing.

There is in fact a fault that needs to be corrected on these parts. When the vendor who made almost all of the Japanese OEMs' vintage clutches created the steel discs, they stamped them with a pattern of tiny indentations. They look like center punch marks. They are likely there to retain oil so the clutch more smoothly engages and disengages. The problem is, the punch marks (technically, "spanking") raised metal on both sides of the discs, which reduced the discs' total effective surface area. Thoughtful techs began abrasive blasting these discs, not realizing that the abrasive merely followed the contour of the discs' high spots, so that nothing was changed. The problem was not corrected.

The correct solution is to sand the discs lightly, just enough to remove the high spots, taking care to not reduce the discs' thickness and also taking pains to not make the discs wavy, i.e. non-flat. This is best done on a surface plate.

These steel discs have only 17,000 miles on them. Note the high spots surrounding each factory-made indentation,

The discs corrected by sanding on a flat surface. The indentations are still there, but the high spots are gone. Just as importantly, the discs are still perfectly flat after the modification.

The large steel surface plate used in sanding the clutch discs. This is how their flatness is ensured. This is important.

Item: The forged piston myth

Common wisdom on the Internet is that forged pistons are superior to cast ones. I have written what I consider a very balanced article elsewhere on this subject and I will refer you to that article linked below for a thorough discussion of the pros and cons of each piston type. Here I wish to simply bust the "forged is best" myth.

As explained in the more comprehensive article, almost all aftermarket pistons are forged, but not for the reasons one might think. Forgings are predominant due to three interesting facts: that very small production runs means forging rather than casting due to costs; that most aftermarket users are assembling heavily modified and stressed engines needing pistons that can suffer unusual abuse; and that performance engine builders prefer the freedom forged pistons offer of excess material on the crown with which to customize the piston top to their needs, something that cannot be done with minimal-mass cast pistons. Consequently, though they exist, aftermarket pistons made by casting are relatively rare. Forged pistons rule the non-OEM piston world.

However, a blanket statement that forged pistons are better than cast pistons is hugely wrong. There are a number of pitfalls that await the unwary forged piston user.

First, the clearance that the forged pistom must be installed at is often considerably more than that of the stock piston, and this has nothing to do with its intended use and everything to do with the much less stable material the piston is made from. But that's only half the problem with clearance, the first half of bad news. The other half is that no one, including the piston manufacturer itself, will tell you what the correct clearace is! One leading maker has you install the piston at such and such a clearance, but then when you measure the ring end gap and find that it is excessive, it is clear the manufacturer did not really mean it! For this and other reasons, forged pistons are best installed at clearances considerably tighter than most think. But only experience will tell you what that is. If it's any consolation, piston seizure in a four-stroke engine, whatever the piston, is extremely rare. I have known it to happen only in connection with lubrication failure.

Second, the typical forged piston's aforementioned extra crown thickness that is such an advantage to the knowledgeable engine builder is on the other hand a liability to the home mechanic who has no intention of customizing the piston tops. The in this case unwanted extra mass actually brings with it two potential problems. One, it makes the piston excessively heavy and thus dimensionally all over the place and resultingly rattly when it heats up. Or, if the manufacturer has decided for you what valve reliefs you need and has therefore removed the extra mass, and hedged his bet by going overboard in an effort to suit every need, as is sometimes the case, you end up with what in your application will be an expensive, low-compression, "high performance" piston.

And finally, third, many forged piston manufacturers seem to struggle in manufacturing the piston's pin and its corresponding bore in the piston. For example, pins made of lessor grade material than stock and then chrome plated to compensate. Piston pin bores that are either too loose or too tight. And, pin retaining systems that differ considerably (and inexplicably) from the excellent stock method. These are all issues with forged pistons. One maker even dispenses with retaining clips altogether and has you put plastic buttons on the ends of the pins (an obvious low-cost "out")! I have seen what those buttons look like after 10,000 miles. Not inspiring.

Add to this a reputation in the forged piston industry for pistons that are not the highest quality. Outside diameters that vary slightly among the pistons in a set. Finishes that could be better. Grooved surfaces that are obvious attempts to compensate for friction issues. I once knew a machinist at a big name piston manufacturer. When a piston came out a touch undersize, I watched as she actually squeezed it in a vise across the pin axis to grow the piston at its skirt. Uh... There are some excellent manufacturers of aftermarket pistons today, many more than there were 40 years ago. Wossner, JE, and several more. Even CP, a division of the high performance connecting rod maker Carrillo, is one of the newest shining stars. But a forged piston is not categorically better than a cast piston. Better in certain applications. Better when modification is necessary. Better when it is all you can get. But not categorically better in all cases, and for many, not the best choice.

Additional reading: Cast vs, forged pistons, Cylinders done right,   Secrets of high performance ngune building,   Engine assembly

Item: Piston pin offset

Here's another oft-misunderstood bit of techie trivia -- what is piston pin offset for? That is, what purpose does it serve? Let's examine that one.

Modern powersports engine pistons are not mounted on their connecting rods exactly on center. They are offset radially, that is, perpendicular to their rotational axis. In other words, in a vertical, single-cylinder engine, the piston is offset toward the exhaust side of the cylinder. The piston pin hole is bored off-center toward the intake side, usually less than 1 millimeter. But why? It is frequently stated with a sort of bored complacency that the purpose of this offset is to reduce piston slap. The truth is, while piston slap is reduced through piston pin offset, but that is not why engine designers go to the trouble.

From a 1960s-era official Honda manual, this illustration elegantly communicates what piston pin offset is meant to accomplish, the shifting and spreading of the stress peak.
The piston engine has three major parts: crankshaft, connecting rod, and piston. Each has a different job to do. The reciprocating part, the piston, makes the crankshaft, the rotating part, uhh, rotate. The connecting rod is simply the part in the middle. It translates the piston's recip motion into the crankshaft rotary motion. The neat thing is that in the process, it shares in the motion of both. That is, the connecting rod is both a reciprocating part and a rotational part, at the same time. (In fact, when balancing an engine, it is common to divide the connecting rod's weight in two, thus permitting half its weight to be calculated as recip and half as rotation.) The point is, the upper half of the connecting rod reciprocates with the piston, the lower half rotates with the crankshaft, and this is important to understanding the stresses on all three parts, but especially those on the connecting rod.

The piston and its half of the connecting rod stops twice per crankshaft revolution, even though the crankshaft continues to turn. This means the piston and top of the rod also start back up twice. This stopping and starting imposes stresses on all three of the parts, stresses that increase with crankshaft rpm. To reduce these loads, the piston is mounted to the connecting rod slightly offset. This causes the piston to reach top dead center at a different time than the connecting rod, effectively spreading the shock loading over a greater number of crankshaft degrees. In short, the real reason for piston pin offset is that it softens reciprocal loading, permitting lighter more power-efficient parts to be used, and the engines to be capable of higher rpm.

However, there is another phenomenon at work here, a kind of side benefit. Because the connecting rod spends most of its time in the engine at an angle, the piston engine has what is called minor and major thrust. Major thrust refers to the downward-stroking piston's force against the cylinder wall during combustion, due to the rod being angled in that direction. Minor thrust is the piston's thrust against the opposite cylinder wall during compression, because the rod's angle is opposite also. These thrust forces push the piston firmly against the cylinder wall. The important thing is that at TDC, the piston's loading changes sides. In older engines, this flip-flop caused the piston smack the cylinder, resulting in a noise. The piston pin offset in today's engines, besides reducing inertia stresses, does two things that reduce this noise. First, because the piston is mounted off center, the transition from one side of the cylinder to the other is less sudden. There is less impact. Second, instead of a sudden lateral shift, the piston actually rolls from side to side. That is, the piston shifts first at the skirt, then gradually the rest of the piston makes contact, instead of all of the piston at once. It's really a cool deal and again, less stressful on the piston.

To summarize, piston pin offset is first the manufacturer's way of reducing stress on reciprocating parts. It permits these parts to be lighter, which results in more efficient manufacture and less power loss in the engine, as well as higher rpm. However, second, piston pin offset reduces piston slap because it provides a more gradual shift in the piston's front to back loading. Transitional change from major to minor thrust means a quieter engine. And that's pretty cool, too.

Item: The over-torquing of cam holder bolts

The cam holder bolt torque specs in many OEM manuals are incorrect, and using them results in over-torquing leading to bolt failure, and worse, distortion of the cam holder, which can result in cam problems. The factories often specify 12 or more foot-pounds for these 6mm holder bolts, nearly double the proper specification and close to that for a spark plug! This error is of course mindlessly repeated all over the Internet.

Two problems here. First, a foot-pound torque wrench is never the right tool for a 6mm bolt. Deadly. A first-semester tech school student knows better. What was Honda thinking? As with many gauging tools and devices, when used at the extreme ends of their scales they are the least accurate, and you certainly want accuracy when tightening. Not to mention the all-too-handy extra length of a foot-pound wrench that naturally promotes heavy-handedness. Properly short wrench and inch-pounds only on bolts that small, thank you very much. Second, a 6mm bolt threaded into aluminum is never tightened to anything over 90 inch-pounds (equal to 7.5 foot pounds, a bit over half the figure in common use). A lot of damage has been done in this area, especially regarding cam holders. Check out my camshafts article for more information.

Additional reading: Camshafts

Item: Break-in used as an excuse for poor engine assembly

People often excuse the poor cylinder compression of their newly-assembled engine with the excuse, "Oh, it still hasn't broken in yet." This is silly. There is such a thing as break-in, naturally, but on superior design multicylinder Japanese engines, assembled properly, when it comes to valves, there is no break-in, and cylinders and piston rings have virtually none. The fact is, due to the high precision of manufacture and assembly required by these parts, they either don't break in (valves and seats) or they complete break-in as a result of the first engine start (piston rings), so in effect the concept can't be applied to this area of the engine. Bottom line, the cylinder compression of a properly rebuilt engine will be the best it will ever be minutes after startup, before it even leaves the shop. It will not increase with miles.

Why then do Japanese powersports manufacturers specify break-in periods? Two reasons. One, the less precision manufactured bottom end components such as the transmission will slough off some forging and casting flash, wear in a few rough spots, and of course the first oil change will purge out the resulting contaminants from this process. Certainly, that is a real need. But beyond that, reason two, the manufacturer specifies break-in as a chance to catch problems from manufacture: circlips not fully seated, fasteners lacking proper torque, misassembled directionally-oriented parts, misaligned gaskets, seals or o-rings ruptured during installation, and to confirm the quality of such vendor-sourced parts as bearings, seals, chains, belts, springs, etc. Break-in as a concept is more a warranty thing than it is a mechanical requirement. And though it is important, it should never be used as an excuse for inexpert engine assembly.

Additional reading: Valve jobs done right,  Cylinders done right,   Porting and polishing

Item: The early Honda V4 cam nonsense

A lot has been said about the failure mode of first-gen Honda V4 camshafts. I have written two or three articles, and many others' websites have devoted space to it, with most of them postulating this theory or that. Unfortunately, the emphasis on most of the other sites is largely on oiling.

Unfortunately because it just isn't true. Though there are only one or two offered today, at one time there may have been as many as a dozen different oiling kit providers. Oddly (or not so oddly, considering the perverse nature of Internet user forums) these kits exist solely due to a misunderstanding. Someone probably observed that Honda's race team was using handmade external oil lines on its Interceptor-based racebikes. The assumption was apparently then made that this was to counter cam wear (though the race bikes didn't use anything resembling stock cams) and before long, everyone "knew" why V4 cams failed. However, there really is no connection, not on the race bikes and not on consumer's bikes. The race bikes used braided oil lines simply because the stock soldered steel oil lines cracked when the machines were used hard. It was common, according to American Honda, for whom I worked in the 80s. It also happened on a bike I raced.

Ask a career mechanic about lubrication-caused cam wear. Mechanics are not confused on this early V4 cam failure issue. Even without studying the issue, they know it has nothing to do with lubrication, because they know what lubrication starved cams look like. The powersports industry has always offered many opportunities to encounter them. Outside our industry, historically, camshaft wear in overhead cam automotive engines due to lubrication issues is also very well known. There is a huge body of emperical evidence because engine oil producers have long recognized this area of the engine as their greatest challenge, the area of the engine at which specific load bearing is highest and therefore lubrication -- by definition the separation of moving parts -- the most at risk. A mocked up overhead cam engine was even added to the American Petroleum Institute's test process for oil durability rating for this reason. Mechanics know the time of day because they handle engine parts. The auto industry at large knows the score because they had to deal with prematurely worn cams when car engines went to overhead cam design in the 70s. What you see when the cam has worn excessively due to poor lubrication is damage that looks like the cam was turned on a lathe. A dramatic, obvious, cutting appearance, with surrounding areas deeply discolored due to heat. This is not what happens in the Honda V4, whose cams get a more crumbled cheese look.

What then causes V4 cam failure? I have said it elsewhere, but it's the failure of the engine's hard chromed follower that tears up the V4's cams. The chromed surface is beat up and eventually broken through by a combination of high valve lift, tandem followers, and abrasive pits that appear in the cam's surface due to manufacturing compromises. Every engine that has this combination has suffered the same cam failure fate: Kawasaki's ZX900 series are a prime example.

Additional reading: V4 cams: what really happened,   Early Honda V4 history,   Debunking early Honda V4 myths,   Julian Ryder's book,   Camshafts

Item: The myth of porting

Porting. There are two completely different worlds when it comes to cylinder head porting, the false and the real. It's not at all what most folks think.

The world of the lowest common denominator, that characterized and promoted by Internet user forums, is basically a hatchet ethic. You know, cut and slash. The same ethos that has folks cutting their frames and throwing away their airboxes and sawing off their mufflers. The adolescent carving on the schoolbench with a pocket knife. Cut, cut, cut. Kick it down, bust it out, tear it up. Carve it, kill it, blow it out. Kind of a cylinder head enema. Very few understand that the porting practiced by professionals is actually very scientific. That is the second world, the real one. Where flow and area and angles and velocity and more, are the bywords, the metrics. Not a haze of aluminum dust.

Three common pitfalls await the non-professional porting practitioner. One, he must ruthlessly expunge from his mind the idea that porting means wholesale metal removal. Or removal of metal at all. Oftentimes porting involves as much putting material into the port as removing any from it.

Two, the wielder of the porting tool (which by the way is NOT a Dremel and NOT a hand grinder) must value and guard and zealously preserve port cross-section as a dogma, a religion. Changes to the port must not result in a larger port. The point of porting is to put the port and its air on friendlier terms, and this is antithesis to making the port larger. Believe it.

And three, just as with exhaust tuning, though for different reasons, the actual work of porting is really all angles. Angles! Optimizing angles, increasing radii, thinking like air would think. What does it want? Where is it going? What will be its behavior at this point in the passage? Is it slowing or picking up speed? Can it be cajoled, tricked, coaxed? It's a cerebral undertaking. And your first several attempts are a coming-of-age event. Very sobering. Very enlightening.

Nigel Patrick, of Patrick Racing, is a legend in Harley-Davidon drag-racing, a five-time consecutive AMA Prostar champion, an acknowledged cylinder head expert and one-time Cosworth employee who was the first to make a billet head for the Harley-Davidson Evo, the first to CNC port a head, beat V-Rods with his pushrod Warrior and Harley dragbikes, and in the early days did engine work on Russ Collins' team where he was on track to solve Russ' Battlestar Galactica's performance shortcomings with new cylinder heads when that project was abandoned. Nigel also won three roadracing championships for Yamaha through headwork. A recent conversation I had with Nigel, who lives nearby, shed some interesting light on the subject of porting. Among other things, such as confirming my longstanding conviction that 80 percent of effective porting takes place within one inch of either side of the valve seat, Nigel shared that in his view a flow bench isn't really that useful, something I was reluctant to accept. I have done some considerable work on a flowbench and taught mechanics school students how to use the tool for some years. After talking with him however I'm convinced. Nigel's record speaks authoritatively. It turns out that flow-benching as it is done by most people is misleading at best. The reason, says Nigel, is no flowbench moves the test air anywhere as fast as the air in an engine actually moves. Thus results do not connect with reality. Nigel told me the only flowbench he would have any confidence in is one he knows of that uses a wind-tunnel-sized blower and thereby pushes air at close to the speed that an engine does. Interesting. For fun, check out a January 2018 interview Jack Korpela/Nigel Patrick here.

Item: The popularity of gauze type air filters

Hint: This is listed in the engine section instead of the carburetor section for a reason. Gauze air filters marketed by K&N, BMC and others, are unbelievably popular. About every fifth customer of mine comes to me with a bike having a K&N air filter. It's hard for me to understand how after all this time the public at large could still be so unaware.

The gauze filter was first sold out of a Kawasaki shop in Riverside, California. Its initial use was legitimate, as a race-day filter that could slightly boost power. The fact that extra airflow was gained at the expense of greatly reduced filtering was a non-issue to racers who rebuilt and changed their engines often, and to whom the idea of 30 to 50 thousand miles of commuting and touring with only light regular maintenance wasn't even on the radar. I have no argument with the gauze filter used in its original, legitimate role. The mistake in my view was when this racing only part began to be marketed and used as a high performance replacement for the stock street bike air filter. There are three reasons I recommend against gauze air filters.

First, they're not filters! They're called generically "gauze" filters because that is what they are made of, loose weave medical gauze, covered with steel screen door mesh. The gauze is of course oiled to make it sticky and expand slightly, improving its filtering ability. But the truth is a lot of dirt passes through a gauze filter that would never get past any other kind of air filter. So much so that the industry has for years now been observing large bore four-stroke offroad singles with badly accelerated cam chain wear. The symptom is poor engine performance and the telltale is a good cylinder leakdown number but low cylinder compression due to retarded cam timing. I have witnessed this firsthand, and it is well known within the industry.

Second, gauze air filterw really don't last all that long. Even properly serviced and maintained, your gauze air filter will gradually deteriorate and more importantly, get dirtier and dirtier and eventually reach a point at which it will not come clean any more. Did you say 100,000 mile guarantee? Not if you don't use the factory cleaner and oil. And even if you do.

Third, gauze air filters seriously disrupt carburetion. Whether a drop-in type filter element replacement or individual filter "pods", the proof if needed that gauze filters pass more air is in how much they alter a carburetor's air/fuel mixture -- an incredible amount! Even the drop-in changes things somewhat, and the individual filters can change things so much that the main jet must be sized up some 10 sizes. Yup, ten.

Additional reading: Powersports air filters,  More on air filters

Item: Honing cylinders

Two things seem to come up often on user forums: honing cylinders whenever a piston is removed and replaced, and honing cylinders with a straight hone for ring seating purposes. The mechanic in me cringes whenever I read this stuff!

First, when to hone a cylinder. If using the same rings, on the same pistons, in the same cylinders, it is not at all necessary to hone the cylinder. In fact, it's a bit of overkill even when the rings are new. It is not mandatory. New major OEM Japanese powersprts brand piston rings are tin coated for break-in purposes. That coating will wear off pretty quick, whether the cylinder is honed or not.

Second, and more importantly, the hone used for this purpose is NEVER the straight bladed type hone. The fact that no one on forums realizes this just baffles me! All you have to do is understand how tightly assembled OEM Japanese powersports pistons and cylinders are to realize the problem. Ten seconds use of a straight hone can double your engine's prescribed piston-to-cylinder clearance! The result will be faster wear, increasd oil consumption, and increased noise and crankcase blowby. And yet highly thought of forum "experts" have no qualms about suggesting this.

Additional reading: Cylinders done right

Item: The pervasiveness of the use of silicone sealer

A motorcycle magazine editor once said he didn't see the problem with using silicone sealer. Two things seem obvious to me in this. One, it acknowledges there is pushback, and there certainly is. In my almost 45 years in this industry, I can't think of anything that says "hack" more than silicone sealer. And two, it only emphasizes the lack of credibility of mainstream powersports media.

When I was in the service trenches in dealersips and independent shops, a good way to lose the respect of your shop companions was to let them see a tube of silicone sealer in your hand. We're talking major problem here.

Blue silicone worms, on the oil pump pickup of a SOHC Honda 750. A sad sight, but at least the screen caught some of the crap. This scene is just as I found it. Nasty!

There are many kinds of sealers used around engines. BMW even had one (Dirko) that was nearly epoxy-like, and actually came with their car's replacement head gaskets. And then there's Rolls Royce specified Hylomar, at the other end of the spectrum in its never-hardening, forever tacky, chewing gum-like consistency. Different products for different uses, right? Naturally. That's decision number one: the right product. But, you ask, don't Honda and the other Japanese manufacturers use silicone sealer at the factory? Yes, unfortunately, it appears they do, despite their specifying non-silicone sealers in their literature. Countless times I have uncovered the presence of silicone sealer on warranty jobs. But there is a real problem with silicone sealer, and that is it has no surface tension. The bit that squeezes to the edge of the joint can't stay there. It has to fall into the oil supply, and that little bit will be there no matter how sparingly you use the stuff, for another issue with silicone sealer is its lack of body: it is impossible to avoid squeezing it to an almost nonexistent film.

Proper sealers intended for use on engines, including the one Honda recommends (but doesn't seem to actually use themselves) have excellent stay-thick characteristics, and the squeezed portions stay attached because the material, unlike silicone, is non-hardening. It stays tacky, in other words. Hondabond #4, made by Threebond and actually the same as their #1104 product, is the real deal. I won't use anything else where engine covers are concerned.

Additional reading: Mechanical bad practice

Item: The "Line bored" swirl

Another topic I have written about on my site, this item is simply how line boring has become a favorite subject among forum antagonists, who like to blame the supposed lack of it for early Honda V4 engine failures, and blame the presence of it for supposed non-interchangeability of those same cam holders on all models. Both ideas are false, as you might expect. Line boring is simply a straw man for their intended invective.

First, let's get the term right. There is no such thing as "line boring." The correct term is align boring, and it simply refers to the process of boring a round passage longtitudally. In simplistic terms, it is used to describe how a removable cam cap can be machined at the factory on the same center as the corresponding machined surface under the cam in the cylinder head.

The trouble on forums is that is that the "experts" assume all engines having removable cam caps are necessarily aligned bored, when in fact they are not. First generation Honda V4s present a fine example. The round surface in the cylinder head and that corresponding surface in the cap cap are produced in separate operations. The two parts are NOT align bored. Some Internet pundits, acknowledging this fact, then use this to explain why these engines had cam issues. Which is just another error as the cam bearings had nothing to do with those engines' cam failures. See the articles linked below for more on this.

Other forum despots then go on to pontificate at length as to how because of align boring it is impossible to take a cam cap from one engine and put it on another of the same model. But here again, an error is introduced. This is far from the truth. Align bored or not, the cam cap on an early Honda DOHC four or CBX, a Honda V4, any number of Honda, Kawasaki, Suzuki and other overhead cam engines, can indeed be put on another cylinder head of the same model, without problems.

Once again, this is one of those things that only Internet jockeys, more educated and smarter than mere motorcycle mechanics, concern themselves with. No career mechanic believes it. He has disproved it firsthand many times over, for one thing.

Additional reading: The myth of line boring,  Inside Honda' first-gen V4s,  V4 cams, what really happened,  Debunking early Honda V4 myths,  More on early Honda V4 cam failures

Item: 1970s Hondas' supposed inadequate charging systems

This is a page from the very earliest factory CB750 manual. You will note that it promotes and legitimizes the idea of adjusting the charge regulator to suit conditions. Don't let the forum "experts" tell you this is a bad idea.

This one gets me, it really does. Vintage Honda forums consistently warn their readers about the inadequacy of 1970s SOHC four charging systems. In no uncertain terms, it is gravely asserted that even a quartz headlight will tax your system unduly and result in your being stranded by the side if the road! What nonsense! I mean, do these folks really believe we struggled with this back in the day? It's ludicrous! I have written about this elsewhere but here are two things to consider.

First, electric clothing use was far from widespread back in the 70s. Certainly it was nothing like it is today. You can't blame the bike, calling it poorly designed, if you insist on plugging in electrical clothing that equals or exceeds its electrical capacity!

Second, for some reason Honda riders of the 70s seemed to more naturally intuit that their bikes were designed to be ridden between 4,000 and 6,000 rpm pretty much all the time. Hondas have historically been tuned like this, at least until the mid 80s, and not just the sport models but all models. It is only in modern times that this seems to have been forgotten. Forum members seem oddly disposed to ride at 2,000 to 3,000 rpm, just a bit above their charging systems' breakeven speed. Neither my CBX or my 500 Four do I ever get into 5th gear in town. Never. And often not even 4th. Why would I? Hondas designed in the 70s are spinners. They don't have any pull until 4,000 rpm.

Third, if my experience servicing vintage Hondas back in the day (and now so much later) is any indication, all or most of the folks complaining about battery charge either have Walmart quality batteries in their bikes or need to get after their bikes' electrical connectors, or have failing parts in their systems.

Although some forum members admit to having complete confidence in their bikes' charging systems, their reason and sensibleness is totally discounted by certain very vocal forum "experts" who feel they must determine what you believe, and want (angrily) you to believe that the fact that 70s Honda fours don't charge at idle is a factory defect. Where does this nonsense come from? The CB500K1 I rode back in that day (and the K2 I own now) had not only an 80-watt halogen headlight, but also high output ignition coils and points set to maximum dwell, not to mention an alarm system and Fiamm horns, and never suffered from a chronically low battery. Owners of these bikes didn't worry about their bike's batteries. I was there! We rode the damn things! Utter and complete bs!

Postscript 2018: I see this week they're still at it, telling innocent people that their bikes won't support even high performance ignition coils! What rubbish! Some are even being led to believe their malfunctioning charging system can be solved only by acquiring one of the handful of complete charging system modernizing kits. This nearly makes my mind explode.

Additional reading: Powersports chrging system history,   In defense of old chrging systems,  Troubleshooting SOHC Honda four charging systems,  Adjusting the SOHC Honda regulator

Item: The high performance ignition coil cult

One of the more interesting fallacies found on the Internet is that of high performance ignition coils. It is essentially a cult, this camp of believers in the magic of increased plug voltage. I actually shudder whenever I see them on a bike in my shop, or hear of them in a forum post in which the poster mentions them as one of his modifications. Why this reaction? Well, it's not because they are good for nothing. They are. But, consider two things. First, the truth is, on a pefectly maintained motorcycle, one correctly adjusted and carbureting properly, the potential for high peformance ignition coils adding anything at all to performance -- that is, smoothness, acceleration, starting ease, power, torque -- anything at all, is very close to nil. It's just a fact. Second, and this is more important, I dislike seeing high performance ignition coils on bikes because they are almost never installed properly. Let's explore these two things in some detail.

Modern fuel injected motorcycles mostly have "stick" coils, known in the industry as COP or coil over plug coils. These bikes have the COP coils because the fuel injected bike often has computer controlled ignition as well as fueling, and part of computer control over the ignition includes in many cases individualized control and timing of cylinder firing. In fact, this is COP's main advantage: independent, on the fly variable ignition. Neat stuff! What many don't realize however is that COP coils are also considerably weaker electrically than the old conventional coil that was bolted onto the frame. This is due to an interesting fact: fuel injected bikes don't need strong ignitions.

Interestingly, ignition and carburetion have an inverse relationship; they are interdependent opposites. When one is lacking, the other can make up for it. The closer to perfect an air/fuel mixture is, the less is demanded of the ignition system, and the stronger an ignition is, the looser carburetion can be. Thus fuel injected engines, with mixtures hundreds of times more precise than what carburetors can manage, get by with less vigorous spark. High performance ignition coils emerged and thrived in an environment in which fuel mixtures were much less accurate due to their coming from carburetors, even more so on models having certain carburetor compromises, and more yet on carbureted bikes that suffered from poor or inexpert maintenance or modification. The fact is, high performance ignition coils' higher plug voltage allowed larger plug gaps which in turn compensated wonderfully for imprecise fueling. Yep. Cycle Magazine had it right. K-Mart coils really did smooth out the average Yamaha RD350!

And just as important, higher voltage coils also compensate, to a great degree, for uninspiring engine performance brought about by poor maintenance. Improper adjustments, low compression, inadvisable aftermarket parts and other ill-conceived modifications -- things of this sort can make a set of high performance ignition coils seem like a silver bullet. But obviously the bike's shortcomings should be corrected instead, and when they are, you will be hard pressed to detect any benefit from the high outout coils. It's a fact.

But the second and more egregious thing about high perf ignition coils is, folks invariably use bad practice when installing them. They're installed with automotive suppressive type plug wires. Or their plug wires are crimped. Or their primary wiring is crimped. Or if installed as part of a complete ignition system package, all of the connections are poorly made, especially those to power and ground.

Is there no benefit at all then? Actually, there is. Having more voltage on tap means the voltage required to bridge the spark plug gap gets there faster, leaving less time for voltage diversion through the spark plug's inevitable carbon deposits. Higher voltage coils keep the plugs cleaner. However, as with everything else, even this benefit is neglible unless your bike has trouble keeping its plugs clean, which no vintage Japanese four-stroke in good fettle does. So....

The almost unthinking installation of high performance ignition coils is one of those things I like to call low performance mechanics. That is, the individual assuming a better than stock result when in reality the outcome is not even equal to stock. There's a lot of this out there in the aftermarket world. There is nothing wrong with high performance ignition coils installed properly. But neither are they the $200 route to better than stock performance most think them to be.

Item: Checking charging system output with a voltmeter

Much needs to be said, and many articles are to be found on my website. But here in a nutshell is the illogic of what so many are doing and saying. Why, when measuring battery discharge, do many correctly use amps, but when viewing things going the opposite direction, i.e. charge, suddenly volts is preferred? I can't make any sense if it! Discharge and charge are the same thing, just moving in different directions.

The fact is, volts is not charge, it is merely the state of charge, the end result; how high the water has risen in the sink, not how fast it is filling the sink. If you want to know a battery's state of charge, measure volts. But if you want to know if, when and how quickly the battery is being charged, amps is the only way.

It should be obvious and only logical that if you check energy leaving the battery in amps why would you switch to volts for measuring it in the opposite direction. But it seems to not be obvious. So here are five more reasons why measuring anything having to do with charging in volts is not correct.

  1. There are at least five completely different kinds of batteries found in powersports vehicles. The correct fully charged terminal voltage of these batteries differ by virtue of their varying technology.
  2. Related to the above, there are four different types of electrolyte used in batteries, each with an increasing density as indicated by that classic tool, the battery hydrometer. Thus no one correct terminal voltage can be said to be valid for all.
  3. Battery manufacture comes into play also. The bargain batteries, made by the lessor quality manufacturers, are less efficient and less productive. This must also be counted against the theory of measuring battery terminal voltage looking for a particular value. Not going to happen.
  4. The amp/hour rating of a battery, in very rough terms equal to the battery's physical size, results in varying terminal voltage when considering two batteries of very different size. Just one more reason there is no one-size-fits-all correct battery terminal voltage.
  5. How the battery is born. That is, how the shop put the battery into service for the first time. There are well established best practices that include periods of soak time and charging time before the battery is installed into the vehicle. The faithfulness with which these best practices are followed naturally varies. The result, according to the manufacturer, is well defined percentages of lost battery function and efficiency. This will of course result in different "normal" terminal voltages.

Something that should become clear after considering these things, and is just another way of saying what has already been said, is this: when all is said and done, the reason voltage should not be used to test a charging system, is that voltage is battery dependant. In other words, a voltage reading at the battery's terminals is subject to the battery itself, whereas a current (amps) reading is measuring the system as a whole.

Additional reading: Volts vs. amps,  The three dimensions of electricity,  The electrical connectors scandal

Item: Relying on resistance tests for electrical troubleshooting

Resistance tests are not best practice in powersports troubleshooting. The top mechanics, those whose walls are papered in certificates and who spend a lot of effort and resources each year to keep up, to improve and to become more proficient; who have a lifetime of day in and day out real-world experience, having to feed themselves and support their families, know this. It is not debated among these professionals. Only those who, though lacking any history of workng on motorcycles for a living, continue to mock and act condescendingly, whatever their supposed qualifications to speak on the subject, that disagree. There are three real problems with resistance tests.

One, the low voltage that a meter operates on when measuring resistance isn't enough to put a load on, i.e. stress, the part being tested. This is important. Wire windings especially, which in the form of charging, ignition and starting system parts make up at least two-thirds of your bike's electrical system, fail mostly by overheating and thus losing their lacquer insulation in spots. This failure has the tendancy to demonstrate itself only when the winding is stressed by current flow. When unstressed, many times the surrounding still intact lacquer is enough for the part to pass a resistance test. This is so common it is anecdotal.

Two, an ohmmeter of the kind used in automotive work is not a terribly accurate instrument. Most manufacturer's manuals acknowledge this by first teminding you that temperature and humidity affect readings, then by insisting that their specifications can be attained only through the use of their recommended model, brand and year of manufacturer multimeter, then even suggest that a part substitution be performed to back up the meter reading! Whatever this is, it is not confidence in the process on the part of the manufacturer. Nor will it be inspiring to the careful reader.

Third, a resistance test is a static test, meaning it is made with the part disconnected and isolated from the system and thus the system dormant. Modern thinking (actually revived thinking from generations ago) says the better test is with the system intact and operational. This "dynamic" test is not only more sure and accurate, it is a lot faster too. Professionals stick with dynamic tests whenever possible. Their job and their livelihood is on the line when they make incorrect diagnoses.

Additional reading: The case against resistance tests,  The voltage drop test,  A plea to would-be charging system troubleshooters

Item: 1970s and 1980s Japanese bike alternator connectors

Most fans of vintage Japanese motorcycles are familiar with the melted alternator connector issue on these bikes. It's common and it's easy to fix. But if you want it to stay fixed you need to know what causes it in the first place. And it's not alternator or engine heat, as many on the Internet suggest.

I am assuming your repair of this connector isn't going to look like simply trashing the connector block ("cannon plug") and splicing the alternator and wiring harness wires together. Folks do that, and it works, obviously, but is that really what you want? Pretty hack, that. The best repair is to replace the connector, sourcing it from one of a dozen sources, and taking two special, additional steps that will prevent that new plastic cannon plug from ever melting again. There are two reasons the plug melts on nearly all large bore vintage Japanese bikes, and going after those reasons are our two steps..

One, the plug, unlike modern ones, is open-backed. This means it is exposed to the elements. Connectors made after 1990 are rubber sealed at the back. They're called "waterproof" and came about due to the need for better quality connectors with the widespread emergence of fuel injection on motorcycles. So the connector is unsealed. That's problem number one.

Two, added to this, the metal conducting terminal inside the connector is attatched to its wire through mere crimping. While a common thing even today (whole wiring harnesses are still crimped), it's really not best practice and combined with the exposure to atmosphere creates a problem. All of the crimps throughout the harness age and oxidize. But the ones at high current spots start getting hot, the actual crimps that is, because the terminal's resistance, which should be neglible, builds up at the corrosion point, the crimp acting like a load, like a tiny light bulb, making its own heat. This increases until the plastic connector starts melting. This is what actually happens. But you can prevent it after replacing that melted cannon plug. You do this by addressing the two issues: the plug's exposure to the elements, and the terminal crimping,

So here's how we fix this. After cleaning the wire to terminal junction, i.e. the crimp, of dark oxidation, apply a rosin-based wire cleaning paste and using good electronic solder such as Kester 40/60, carefully solder the terminal to its wire. This doesn't mean solder the alternator wires into the bike's wiring harness. No, just solder over each wire crimp. This will enhance conductivity and isolate the crimp from exposure to oxygen. The second step is to go a liitle further and fill the whole open back of the connector with grease. You have probably heard of doing this, and folks get anal about the type of grease you're supposed to use, but really any kind will do. Just don't use something so thin it's like Vasoline. Too thin. Ordinary wheel bearing grease has always worked great for me. Doing these two things is a permanent, factory-like repair. The alternator can still be unplugged at any time for testing or replacement. And you'll never have to think about that connector again.

Additional reading: The electrical connector scandal

Item: The retrofitting of stick coils

This one blows my mind. But it is an excellent example of the myth taking the place of objectivity that characterizes much of Internet forums.

Ignition coils as found on powersprts vehicles are either high tension or low tension. High tension (tension is really an engineer's way of saying voltage) coils are easily identified: they have one or more very thick spark plug wires. Low tension coils on the other hand have no spark plug wire. That is because low tension ignition coils are built into the soark plug cap. Neat, ultra-compact, and slick. Low tension coils are what are found on an increasing number of vehicles. But here is the catch. They are very low-powered coils. Their strength is not in their voltage (low tension, remember) but in their compactness.

Low tension coils (often called stick coils or coil over plug coils) actually emerged on motorcycles during the period of transition from carburetors to fuel injection. They are used today for two reasons. Their compactness is one. More importantly however they are computer controlled and computer-friendly. That is, the bikes' onboard computers can operate them independently and uniquely, resulting in independently contolled engine cylinders. That's right, timing that is tailored to individual cylinders. And they are computer-friendly in that, without dangly high voltage plug wires, reduced radio frequency interference (RFI) results, which is a better thing around microprocessors.

Here's the thing. Folks fitting stick coils onto their carbureted bikes are reducing not improving their ignition's performance. These coils' lower spark voltage is less suitable to the more roughly metered fueling of a carburetor. They were designed to be adequate for the far more precise fuel injection models they come standard on, which fuel injection tolerates their low performance just fine.

Additional reading: Powersports ignition evolution,  High performance ignition coils

Item: The assumption that dual-output coils fail only both outputs, never just one

This is a perfect example of experiential knowledge trumping, as it always does, the parroting of theory. It also exemplifies the very thing that is wrong with motorcycle-oriented user forums: most of what passes for knowledge is borrowed from the 'net or handed down in some other fashion, and not legitimately earned, that is, not something known by the poster through firsthand experience.

As far as how a dual-output ignition coil works, it's true, since the two plugs fire in series, the failure of one of the outputs either at the plug or elsewhere on the coil's secondary side, should result in neither output working. However, although a failure usually happens that way, it doesn't always, and the industry has known this for 50 years at least. When one side of a dual outout coil fails, the electrical strain built up in the secondary winding wants badly to return to its source, the battery, and will try hard to find a path. What can and occasionally does happen is the secondary winding will arc internally, inside the coil assembly, back to the primary, thus allowing one output to work while the other does not.

Two interesting things. First, this possibility of internal monkey business is so strong that it is why you never want to remove the plug wires from your plugs and crank the engine, without first defeating the ignition system. You'll note that Honda had kill switches way back in the 60s (and still do) do that very necessary defeating for you while still allowing the starter to work. The other brands' kill switches used to defeat the starter as well as the ignition (though they caught up to Honda during the early 1980s). Not so handy. Second, this tendancy for the coil to arc internally is why BMW boxer ignition coils had special "lightning rods" built into them. The only ones to do so to my knowledge, and for a very special reason. Ask if interested.

Item: Reusing ball roller type wheel bearings

Another incredible finding on powersprts user forums. Trade schools everywhere train against this notion. It is not good practice.

Two kinds of roller style bearings are found in powersprts wheels: ball and tapered. The good news is that as long as the vehicle is never pressure-washed (don't!), the grease used at the factory is lifetime, it never needs to be replenished. Naturally this does not take into account the now 40 to 50 years many popular vintage bikes have been around. Mere attrition has caught up with them by now -- definitely service those wheel bearings! But you get the idea. During their normal service life, the silicone based grease used in Japanese (at least) steering and wheel bearings is extremely long lasting. A dozen years without added lubrication is nothing.

And that's a good thing, because when talking about ball type, removing the bearing to regrease it is not correct practice. The only way to remove a ball type wheel bearing is to drive the bearing out against its inner race, as the outer race is not accessible. Since the bearing seats in he wheel against its outer race, this means the hammering force must go through the balls, and of course both races. Even the best quality bearings will not take this treatment without harm, for two reasons.

One, ball type bearings are designed to support loads mostly radially, with only a marginal ability to accept lateral loading.

Two, although bearing manufacturers could make bearing races that resist indentation, they don't because such a bearing would be too brittle to be safe. So pounding on the bearing to remove it necessitates its replacement. If it's a ball type. If tapered, such as what Harley used for many years, that's a whole 'nother story. The inner race and rollers come right out with no force, and Harley themselves prescribes a 10,000 mile regreasing interval. But again, that's just their tapered bearings. Their current ball type wheel bearings and all other ball wheel bearings are replace-only, you never repack them.

Item: Use of thread locker on fork damper rod bolts

A nuisance to begin with, the unwary mechanic with ruin his tools, or worse the bolt, trying to get it out when someone prior has used thread locker. Shudder!

Another example of the excruciatingly real clash between the weekend mechanic and the career dealer tech, this one. I am alarmed at this trend of specifying the indiscriminant use of thread locker.

Yes, I am aware that at least some official Honda manuals include putting thread locker on those Allen-headed damper rod bolts, but I find this terribly amusing, in the same way watching someone step on a cat's tail would be.

First, Honda never, ever put thread locker on their 70s and 80s street bike forks at the factory. Why that is found in some of their manuals is really curious. We career techs used to moan about why couldn't Suzuki, who did put thread locker, be more like Honda, whose forks could be disassembled without first using a gas torch on the bottom bolts, as you had to do with Suzukis.

Second, and this is the main point, you have to understand what thread locker does and how you have to work with it. It wasn't that we were lazy. It's a matter of putting your wrench on the bolt not knowing it is Loctited and promptly buggering the hell out of that delicate Allen head. You think this is of little concern? You wouldn't if you had to spend a couple hours or even a whole day trying to get a trashed damper rod bolt out! If a mechanic knew that a fellow mechanic had, however innocently, set him up this way, he'd probably throw a wrench at him!

I may have replaced the tube of Loctite I had in my toolbox once in over 20 years as a Japanese bike dealer tech. It was used only for camshaft sprocket bolts and shift linkage parts, and not much else. Certainly not fork bottom bolts!

Item: Recamming drum brake actuating arms

In yet another instance of supposedly more savvy bike builders actually knowing far less than the average dealer tech, I often see on Pintrest, in magazines and elsewhere, the telltale oddly-angled rear drum brake actuating arm indicating dangerous arm recamming.

A drum brake has two important pins. One (if standard single leading shoe type) acts as a pivot point, against which the brake shoes pivot outward when applied. The other is the actuator, a cam that rotates and causes the shoe pivoting and thus expansion against the wheel drum. A lever or arm on the outside of the drum is connected to this cam, and a rod or cable to the arm, until we get back to the rear brake pedal that starts the movement in the first place,

The actuating arm is splined to the expansion cam on most Japanese bikes, certainly all the Hondas of my acquaintance. And although there is a dot on the Honda part at least to indicate where the factory clocked the spline, it is nonetheless possible to ignore that and spline the arm any way you want. Many folks in the 70s in particular quickly discovered the advantage of splining the arm backward a few degrees to gain a few extra miles of brake shoe wear. There is a pretty serious problem with doing this however. Honda deliberately made the actuating cam impossible to over-center, that is, rotate too far, when the parts are properly assembled. The cam will rotate only 50 to 60 degrees. A repositioned, or as I called it, recammed arm will increase cam rotation to in many cases 90 degrees and put the part in real danger of locking up the brakes. If this, despite widespread practice, had never happened we wouldn't be discussing it. But it did, and it can. Don't be ignorant.

Item: The use of premium fuel in standard model vintage motorcycles

I guess you have to have been there, on the inside of the industry to fully appreciate how obvious this is to most of us. The fact is, vintage Japanese streetbikes were all designed to run on 86 octane unleaded gas.

Forget octane. Modern combustion chamber design has made that a non-issue. And never mind oxygenates such as ethanol. They have nothing to do with anything. What we are talking about is the chemicals and detergents added to the more expensive "premium" pump gas. They are not friendly to your mid-1960 and later Japanese standard powersports vehicle.

When a dealer tech I once observed a GL1000 whose exhaust valves were so carboned up (on their stems, particularly) that upon deceleration from a certain engine rpm the valves would delay closing slightly and the pistons kiss them closed. True. And not only that, I have witnessed countless numbers of removed valves that were almost unrecognizable due to carbon buildup. What causes this is the lubricants that are a part of "geezer gas", i.e. pump premium. That fuel is only there for the odd Anerican V8. It has no place in a more modern engine such as a Japanese overhead cam multi.

It's hard to convince some folks, especially those who want "nothing but the best" for their bikes. But using a gasoline that can't completely burn and leaves behind tons of garbage is doing your engine serious harm. Now, there are exceptions, of course. Hypersports bikes such as the ZX-14 and turboed or supercharged models, four stroke motocrossers such as the KX450F -- of course these machines need a higher octane fuel and that is specified by their manufacturers. No argument there. In view however are all the vintage standard models: CB750s, KZ1000s, GS1000s, XS1100s. These are 86 octane unleaded vehicles. Always have been. Treat them right.

Additional reading: Octane,  Gasoline,  Valve jobs done right

Item: The silicone brake fluid controversy

And controvery it is. On user forums, this topic generates, as does oil threads, a lot of heated discussion. There is usually more heat than light, in fact. No doubt some of this is from bad experiences, but also some is simply ignorance, parrotting what one has read or heard, which is in fact how many arguments ensue on the 'net.

The telltale purple color of silcone brake fluid. Pretty, no? You'll like how it treats your aluminum brake parts even more.

I have written a much more exhaustive article on this, so see that article (linked below). The gist however is that hysteria is finally giving way to reason on this issue. More and more folks are discovering the truth for themselves. Silicone brake fluid is actually the best thing to use if A) your rubber brake components can abide it, B) if you value lack of corrosion to a great degree, and C) if the potential for slightly reduced brake feel is acceptable. Let's explore these three things.

Rubber brake parts, it seems is the number one bugaboo. This in fact was the original argument against slilicone fluid and it may still be the strongest one, despite many advances in silicone fluid and in brake system parts over the years. My own experience has been with Honda and Kawasaki brake systems only, and so far I have not seen any compatibility problems. Seals and o-rings don't swell or react. Nothing bad happens. Others however report issues. I personally feel that both OEM and aftermarket brake seals and o-rings have either always been good enough (OEM Honda) or have improved enough that this is a non-issue. While I don't discount others' findings, I feel there is no cause for worry. However, I have found certain aftermarket rubber parts are so bad, so poor, that ANY brake fluid, of whatever kind, does them serious harm. K&L parts in particular have been giving me trouble. I have since located a Viton rubber seal that I use to replace its counterpart in the K&L kit, and that has worked great for me.

Silicone's absence of glycol fluid's self-destructive nature is its real boon for vintage bike brakes. The gearhead Corvette, Chevelle and Mustang owners swear by silicone fluid, and an increasingly wider group of motorcycle owners do as well. If you like not having to regularly rebuild the brakes on a powersports vehicle that gets very infrequent use, silicone fluid is for you.

Increased compressibility. I am not convinced this is a real concern. I mention it because historically it has been presented as one of the big negatives of silicone fluid. Racers in particular stopped using silicone fluid because of it. Yet, I have never detected any difference in brake function or feel between glycol and silicone brake fluids.

As far as I am concerned, there are virtually no negatives with silicone brake fluid, despite all the heated, pontificious rhetoric. No one has heard more of the arguments against it than I have, being a technician trained and employed by Big Five powersports manufacturers all my working life. Read my far more extensive article, and keep in mind this is one of those topics folks like to get on their soapboxes about, even when they have few or no facts.

Additional reading: Brake fluid

Item: "Blued" exhaust pipes

It's called blueing, but a better term is discoloration, because the color of the coloration is not always blue, but often black. That's important, but not all that much. But just for the rcord, it's mainly aftermarket pipes that blue (OEM Japanese exhausts of the 70s and 80s are double-wall, making them seldom blue, though in extreme cases they still do). Stainless steel exhausts are the ones that mostly blacken.

To the point, many times I read on user forums folks linking discolored exhaust to all sorts of engine conditions, tuning, etc. As if exhaust discoloration is a defacto indication. Possible, but not often and really seldom when the exhaust is, as is most common, uniformly and thoroughly discolored. In those cases the cause is something far simpler and more basic than vacuum leaks or other maladjustments.

When all the exhaust pipes are equally discolored, the cause is almost always linked to an unsteady idle and often one that hangs up at high rpm. That would be the engine tune issue. Carbs out of sync, one or more carbs overflowing, that kind of problem. More often though, the cause of exhaust discoloration is choke misuse, resulting in the idle creeping up too high. Honda even used to warn in their bike's owners manuals not to let the idle rise above 2500 rpm, because of the blueing problem.

In my experience, when the discoloration is even across all the pipes, idle abnormality is the reason, and improper use of the choke is the most common cause, though carburetor malfunction is also possible.

Item: Vehicle identification numbers (VINs)

Okay, so this one's a little on the picayune side, but I'm feeling a little grumpy today, so... VINs.

All over user forums I see serial numbers and VINs confused, usually with folks calling everything a VIN, as if it were just another name for a serial number, a kind of shorthand or nickname. I understand the tendancy. But the two things are completely different, to those who know the difference, which I admit isn't everyone. But bear with me.

A serial number and a VIN are very different animals. Until January 1981, manufacturers weren't actually required to even have an identifying number on its vehicles (nor, incidentally, are manufacturers required to have warranties, even today). Having a serial number, and here we mean an identifying marking on the vehicle's frame) was completely voluntary. But of course all manufacturers had them because it was useful for their own internal record-keeping purposes. However, as you might expect, every manufacturer had their own proprietary serial number system. They could do with it whatever they wanted, code it as they wished, and change it or reinterpret it any way they chose to. Remember, no one told them they had to have one. And of course, this meant no two manufacturer's serial number systems were alike, not to mention that even year to year within a single manufacturer's system there was a lack of consistency. This was the situation with serial numbers. They really meant only what the manufacturer intended, with no outside oversight, and no consideration for communication outside the manufacturer's offices. Secret codes with meanings, if you will, if any, in other words. And, wouldn't you know it, the manufacturer could reuse the same exact markings as many times and as often as they wanted. And some of them did. For more on that particular issue, see my article on the 1975 change in model designations, linked below.

All of this changed in 1981. A few years earlier, late in 1979, US lawmakers wrote a new Federal Motor Vehicle Safety Standard (FMVSS 571.115) in which it was proposed that from the 81 model year forward (giving manufacturers ample time to determine how to comply) frame markings would, by law, actually mean something communicable and trackable. They would identify the vehicle, include engine size and power codes for the benefit of markets such as Japan and Europe where licensing and taxing was based on these, and very importantly, communicate the model year, exact model/body style, the manufacturer's plant, and so on, all for the expressly stated and very real and vital purpose of increasing the number of vehicles successfully recovered and repaired in the all-important and unfortunately rather frequent eventuality of manufacturer vehicle safety recalls. The highest purpose of all. The VIN's reason for being. Up to then, recalls had a much lower completion rate. That is, many more slipped through the cracks. Even today, saturation is never 100 percent. But before VINs, it wasn't even close.

And the VIN brought three other really interesting new things. One, unlike the situation with a serial number, which the manufacturer could repeat whenever they wanted, each VIN had to be absolutely unique for a period of 30 years. That's right, no two VINs could be indentical for a 30-year span, after which a VIN could be repeated (and as of this writing already has). The other significant and actually related new thing, and the most important from a law enforcement perspective, each VIN included an anti-theft code that if altered red-flagged a stolen vehicle. Unfortunately, the anti-theft code has at this late date long been available on the Internet, so that part is a bit of a fail. Chalk it up to the online explosion of information. Third, the VIN, through its model id portion, easily communicates the vehicle as either on-road or off-road. Presumably state motor vehicle divisions would be using this, and most are, though inexplicably, some of them are to date ignoring it and blithely licensing non-DOT and non-EPA legal vehicles for street use, and even worse, not always sharing the fact of this peculiar exemption to their own state's law enforcement agencies. Go figure.

As mentioned, unlike a serial number, this VIN system would be consistent across all manufacturers, because though originating in the US and applying only to street-going vehicles sold in the US, since no manufacturer wanted to be left out of the US market, they all complied, making it worldwide. And since manufacturers avoid expensive single-market assembly lines, even non-US market vehicles received VINs. This is where we are today. In many ways, the VIN could be called the vehicle's DNA. Exclusively unique, traceable, and superlatively informative.

So, to recap, a frame number on a street-legal vehicle marked as a 1980 or earlier model communicates at best only production sequence, i.e. "serial" information, which is why it's called a serial number. A VIN by contrast records not only serial information but much more, by means of its mandatory sections revealing everything but what the assembly line worker had for lunch. Thus, calling a serial number a VIN is technically uber-incorrect and in a practical sense misleading, since a serial number, if it conveys much that is useful at all, is of no informational benefit to the public, but only to the manufacturer. Far from the rudimentary serial number, the VIN is full of information vastly more useful to both parties, plus insurance companies, lawyers, and governmental agencies.

Additional reading: Five powersports related laws that affect you

The naive believes everything, but the prudent man considers his steps. Proverbs 14:15
Do more, talk less. Proverbs 14:23

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