Some interesting facts, advice, opinions and observations about the iconic and special GL1000 coming from a career of familiarity with the model. In no particular order.
Many online voices supposedly experts on the GL1000 frankly are not. None of them have experience in a retail repair and maintenance environment. They repeat false narratives and apocryphal, though popular, posturings; vacuous suppositions whose gravitis rests merely in their incessant telling.
The carburetor's vacuum top and slide are not matched parts. Honda sold them as a set for inventorying reasons, not engineering ones. This is just one of many misunderstandings common on user forums.
The GL1000 is a unique machine whose tuning requirements are unlike any other Gold Wing and very different from other vintage Hondas.
The GL1000's carburetors are derived from those on the earliest Honda automobiles. Many of the carburetors' parts actually interchange. They're odd ducks, technologically.
Official confirmation as well as the vehicle's part numbers prove that this engine was developed by Honda's auto division. Ergo the unusual carburetors, the stepped-voltage ignition, the pressed-in piston pins, the humongous flywheel, and other distinctly car-like features.
The GL1000's ignition system presents the greatest hurdle in tuning this engine. The necessary steps in timing the ignition are completely out of the box and familiarity with any other motorcycle is not an advantage. If you don't know these steps you will not get this engine running its best. And Robert Overby did not invent the correct, split timing method.
The idle jet rules the GL1000 carburetor. No other GL1000 carburetor circuit makes as much difference performance-wise as the idle jet. But it can be a challenge. It is the smallest jet in the carburetor. It is buried the deepest and often difficult to remove. The jet's hole is only 0.013" in diameter, meaning that unless you just removed and cleaned it, count on it being at least partly blocked at any given time. And lastly, the idle jet affects not only idle but also starting, accelerating from a stop, and even cruising--yes, cruising, at low load and low rpm. Nothing is more critical than the idle jet to a pleasant-performing GL1000. Make sure the jet is clean, and this does not mean merely blowing air through it. Also make sure the idle circuit's air bleeds (under the vacuum piston) are the correct sizes.
Forums talk a lot about carburetor slide movement in relation to engine performance. However, they miss three important facts. One, the GL1000's slide does not start lifting until after one-quarter throttle. Two, slide movement in this constant velocity carburetor lags behind throttle position. There is no direct corelation. And three, the ratio of throttle to slide movement is not constant but changes with engine load.
The GL1000's carburetors are actually too large for the engine, especially the 1975 through 1977 model carbs, the largest. The 1978 and 1979 carbs were shrunken, and every four-cylinder Wing after the GL1000--including the 1100 and 1200--was given increasingly smaller carburetors.
Though lacking an accelerator pump, the GL1000 carb set could have used one due its being oversized. But installing the accelerator pump equipped GL1100 carburetors is not the answer. Proper tuning that overcomes the bike's famous throttle lag is.
All of these bikes exhibit low cylinder compression. This is due to valve and cylinder wear. The first is easily remedied, the second not as easily because the cylinders are part of the crankcase and thus more work and demanding of much more skill to machine. Very few people bore this engine as a consequence.
Just as with any 50-year old motorcycle, the GL1000 should not be regarded as a viable touring bike. This may hurt some feelings, but there it is. I am nuts about 70s Hondas. But I would never ride a 50-year old motorcycle very far--certainly not out of town nevermind out of the state. There isn't a single replaceable part on that bike that can be purchased from a brick and mortar store. Not even the spark plugs. Maybe a turnsignal bulb. A fuse. Maybe. Virtually every part you will ever put into that machine will be diligently sought out over long periods online. These are the facts of life with a bike of this vintage. It's a great bike. But its maintenance is also demanding on the order of an obsession.
The number one thing is ignition timing. Don't think you know how. If you haven't done it, you don't know how. And even if you have, you still don't. You need to find out how, and it really needs to be done. But it is far from intuitive. And unfortunately, the need for this adjustment is not reduced by an aftermarket ignition system. Worse, the proper procedure is not explained in the official manual. And it's many times more important than carburetor work.
Close behind ignition timing in importance is the use of the very best ignition parts. This starts with factory Honda Hitachi (or TEC) brand points.
The carburetors aren't difficult to service, but they are quirky enough that familiarity with other carbs won't help much, and mere intuition is likely to simply get you into trouble.
Nearly every GL1000 I see in my shop has poorly-maintained spark plug caps. They are usually very loose on their wires, and inevitably have aged into the 10K ohm range and above and require replacement.
If you have Dyna ignition coils on your bike, you should have been told three things. One, the stock GL1000 ignition coils are just as powerful as Dyna coils (back in the day Honda mechanics fitted them to SOHC fours as an upgrade). So you won't gain any performance from the Dyna coils. Two, Dyna coils come default with automotive type resistive plug wire. Not a good thing on a Honda. You can request non-resistive wire at the time of order and that is what you should do. Or replace the suppressive wires if that is what you have. Three, Dyna coils may be the best coil replacement option simply on the basis of aftermarket quality. But choose the gray (2.2 ohm) ones not the green (3 ohm) ones and gap your plugs at 0.032".
Cylinder compression is vital in this machine. If it's below 150 psi using a quality (not a $49) tester, forget about engine tuning until that is corrected.
The idle jet is critical. It must be removed from each carburetor and "sized", that is, its size confirmed with a wire of known dimension. Virtually all of this engine's operational finesse depends on this jet. It is frequently neglected, and unless very recently looked at, almost surely at least partly plugged. Don't overlook this.
The front brakes require careful assembly of their sliding collet pins, and the application of true, high-content moly grease.
The rear wheel flange demands a goodly application of high-content moly grease. Honda still sells this grease. It comes in a squeeze tube and is also used as engine assembly lube.
Unplug your crankcase breather from the airbox. This will eliminate the otherwise inevitable sludge and carbon formation on the carburetor slides.
Do not use premium gasoline in your GL1000. This engine is already prone to accumulate carbon. Using anything that will accelerate carbon buildup is a bad idea, and this includes that snake oil of snake oils, Marvel Mystery Oil.
Shun carb rebuild kits. No professional carb rebuilder uses them, and no one who cares about their carburetors should either. Kits containing replacement jet needles and needle jets result in the most seriously negative alteration you can make to these carburetors. The Randakk kit is an exception.
One of the bad things about carb rebuild kits for the GL1000, other than the near criminal replacement of factory metering parts with Chinese substitutes, is the unfortunate fact that the o-rings for the primary and secondary main jets in these kits are incorrectly sized and tear when installing the jets. No o-ring supplier and no kit contains the correct o-rings. They are available from only one source, and that source does not sell to the public. Fortunately, finding a business that has an account with this source and will sell the o-rings retail is not difficult. One such retail outlet is Amazon, believe it or not.
The throttle shaft felt seals on the GL1000 carburetor are not vacuum seals, they are dust seals. As such they cannot be expected to solve an engine performance issue. If you're experiencing such an issue, diagnose and go after the real problem.
Twisted throttle shafts are virtually endemic to GL1000 carburetors. It happens when the machine is resurrected from the dead and someone inadvisably exerts extreme force on the throttle grip to overcome the varnish buildup inside the carbs. The delicate shafts easily distort, making tuning of the carbs impossible.
Unless rebuilding your carburetors each season is your idea of a good time, use Sta-Bil fuel preservative. And since the time it takes for fuel to start to gel is less than the period between rides for most of us, use it full-time.
The GL1000 carburetor is very much at risk for corrosion. This is because it is made of a less expensive aluminum alloy rich in zinc, thus extremely susceptible to corrosion. The result is that these carbs can corrode badly. And it has nothing to do with ethanol.
An unfortunate design flaw on these carbs is that they have no overflow telltale system. In fact, no Wing carbs do, four-cylinder or six-cylinder. (Many of Honda's late model carbs-- V4s, CBRs, even cruisers, don't either.) This means that when the carburetors overflow--and they inevitably will--there is no outward sign, no indication. This is not helpful for maintenance and poses a potential deterioration problem for the engine as the engine oil is continually at risk of fuel dilution.
Eventually every GL1000 will start to overcharge its battery. The design of the charging system (permanent magnet, three-phase) coupled with the historically inevitable failure of the voltage regulator, makes this a sure thing. Constantly feeding 16V @ 9.5A into the battery theoretically can make it explode. It can damage the lights also. The only reason that may not happen on your bike is the fact that the GL1000 is a voltage sponge. Its electrical system, and particularly the huge 18 A/H battery, sucks up a ton of energy. But don't count on it. I see this overcharge often, and it is not a safe situation.
Easily two-thirds of the advice on popular GL1000 websites is not good information. Most of them don't even know the purpose of the hoses between the sides of each carb and the air chamber (plenum) and have been debating the necessity of static ignition timing for decades, despite Honda's documented preference and the experience of pro mechanics. And forum-based electrical troubleshooting advice is not real-world. There has unfortunately been a long history of misinformation about this model online, more so than with other model Hondas.
All years of the GL1000 exhibit an off-idle hesitation. Even the better-tuned 78-79 models. There are different approaches to eliminating this performance glitch, all of them easy and effective. But bear in mind one thing: the GL1000 engine will never throttle like a GSX-R Suzuki. This is a car engine, remember, with a massive, manhole cover-resembling, inertia-storing, automotive style flywheel that prevents instant throttle response. But careful tuning can make a significant difference.
Although considered a matter of preference and vigorously and incoherently debated on the 'net, the GL1000 like most 50-year old Hondas is ridden so little that it is an excellent subject for switching over from glycol brake fluid to silicone to prevent brake cylinder corrosion.
Like most 70s Hondas, the GL1000 starting system's archaically-designed, three-roller freewheeling (sprag) clutch is negatively affected by heavier oil and by synthetic oil. Also, long periods of sitting promotes moisture accumulation which results in rust in this part, further deteriorating its function. Watch out for this. The engine has to be removed to repair/replace this part.
The infamous alternator stator connector meltdown has got a lot of press on forums, but in reality it is only one of three electrical connectors on the bike that are prone to failing. The good news is the parts to repair them are readily available and the proper repair technique, while ignored by forums, simple and permanent. Stator failure is not linked to connector failure, despite assumptions.
Rusty fuel tanks are a hurdle on this machine. There are many approaches to repair but removing the tank is best practice.
Proper GL1000 clutch adjustment is typically neglected, what with the restricted access to the pressure plate. Correct clutch adjustment on most Hondas involves a special procedure wherein the cable is completely slackened, then the pressure plate adjusted, then the cable slack removed and a tiny bit of slack left at the operating lever.
Due to the very loose (well over 0.005") fit of the camshafts in their bearings, valve clearance changes dramatically as the camshaft rotates. Perfectly set at TDCC, at 90 degrees (180 on the crankshaft), the clearance will be close to double. Similar to most of Honda's 1970s engines, this is of no consequence, not even excessive noise. And it does not mean the cam lobes are mismanufactured. It's all in the loose fit of the bearings.
One of the most interesting things that reveal the GL1000's automotive DNA is its "floating" piston pin. Something of a misnomer, this means the piston pin does not rotate in the connecting rod, but only in the piston. It is pressed into the rod. In every other Honda motorcycle engine and virtually all other powersports engines the piston pin rotates in both the connecting rod and the piston. A special auto-derived tool is required to remove the pistons because of this.
As mentioned earlier, the GL1000 ignition coils run on two different voltages. On starting, the coils get full power. Then after, they run on reduced voltage. Seemingly another automotive anachronism, no one is really sure why this was done to the GL1000 and defeating this goofy setup actually yields improved ignition performance, with no durability drawback.
The GL1000 has ignition points that look like those in the 70s 450 twin. But don't be fooled. They are not the same and using 450 points results in reduced adjustability and despite what many say, no performance advantage.
Once spied in the text of a European Honda advertisement, it is likely the "GL" model designation came from the words, "Grande Lux", a phrase meaning the pinnacle and which we in the anglo world have irreconcilably and improperly bastardized to, "Grand Deluxe".
The GL1000 lacks an accelerator pump on its carbset. And it can use one. There are even folks who have managed to fit enough Honda car carburetor parts to give it one. And some fit GL1100 carbs which have an accelerator pump. But there is a much better and easier way to get excellent throttle response in a GL1000. This involves several tuning steps, the most effective of which is adjusting the pilot screws to 3 full turns out from gently seated. This makes the idle a little richer than it should be when checked on an exhaust gas analyzer, but it is worth it for the significantly improved throttle response it and the few other special adjustments (such as the 0.006" valve clearance) deliver.
Adjusting the valve clearance on this engine to 0.006" instead of the factory recommended 0.004" will increase cylinder compression by a minumum of 10 psi and likely 25-30, with no drawbacks and an expected improvement in starting and low-speed performance.
There is a significant party of GL1000 single-carb conversion advocates. The truth is that few if any carb conversions go exactly as planned. Carb manufacturers do not make their products easily adapatable to other engines in the sense of tuning parts avaiability and you should know that it can take years to get to anything approaching adequate performance and not many have been satisfied with the outcome. There is therefore no point. Moreover, the original carburetors once prepared properly work outstanding and proponents of conversions are folks who have been frustrated--due to poor work and/or parts--with their stock carburetors. However, the factory carbs are not difficult to service, they just require considerably more than the "dunk and rinse" rebuild ethic.
Although for more than twenty years Honda put valves in their powersports engines that were made cheaply and so soft that they receded rapidly, resulting in such a steady loss of cylinder compression that by 15,000 miles 70s Hondas are decidedly below spec, the GL1000 was an exception. The GL1000 escaped some of this trouble kind of by accident. Though it has the same soft valves as the other Honda engines of its era, its automotive engineers, in specifying unusually (for Honda) soft valve seats, unknowingly gave the GL1000 and GL1100 something of a reprieve from the severe valve recession malady that plagues all vintage Hondas.
The GL1000's reserve lighting unit is a black box that automatically turned on the other beam when one of the headlight's beams failed. The box itself was prone to failure and Honda actually recommended to its dealers that it be bypassed electrically.
The neutral light switch in the GL1000 has a history of failure and according to the service manual requires removal of the engine from the frame to replace. Enterprising techs soon discovered that the switch could be replaced in the frame, with a little loosening of engine bolts and prying with levers. Even Honda capitulated and changed the recommended allotment of time in their warranty flat rate manual.
Eventual head gasket failure on this engine is accepted, with the result coolant ingestion by the engine. Replacement factory head gaskets are now history and aftermarket ones have proven to be much lower quality and unreliable. However, one aftermarket company that reproduces the composite style Honda head gasket is Cometic in Ohio. Be sure to coat the head gasket with Gaskacinch as experienced Honda mechanics have done for more than a half-century.
The GL1000 was subject to the rear wheel hub where the bearings go failing. The steel insert embedded in the aluminum casting worked loose. In worst cases slowly spinning the rear wheel with the bike on its centerstand will produce a rhythmic creaking sound that repeats every half rotation.
Any time the carburetors are off, take that opportunity to replace all the gaskets and o-rings associated with the coolant piping. They eventually leak, and wouldn't you know it, bumping the carbs against then during carb extraction will often precipitate that leakage. Replacing the gaskets especially is a tiresome exercise that you won't want to have to do later with the carbs in place.
Many of you won't be old enough to remember this, but back in the 80s Dunlop investigated reports of tire failures and in their studies, which included hanging out at rallies, they were surprised to discover than virtually every single Gold Wing tire they measured for pressure at half the required pressure. Career mechanics weren't surprised. We have observed this seemingly forever on all kinds of motorcycles.
Don't put an air filter in your Wing that requires oiling. Whether a Uni or a K&N, these kinds of filters cause oil fouling of the airbox that results in the carburetors sliming up, particularly the labyrinth-machined slides.
The ignition timing method that entails mounting a degree wheel to one of the camshafts isn't a bad idea. The technique was shown us at factory Honda school back in the early 1980s. But the advantage of this method is limited to it being a good way to confirm full advance timing. The degree wheel routine was demonstrated in tech school to solve a single problem, which is explained below. Static timing is still the better way in every other consideration.
Honda's Portland, Oregon training center conducted a demonstration in which it was shown us dealer mechanics why early GL1100s were pinging. Their mechanical advancers were over-advancing. This was easily fixed by altering the advancer's stop ears.
Although it is a bit of a chore to properly adjust the GL1000 clutch--just getting the cover off is a challenge--it is very doable. To streamline the procedure use a screwdriver shortened way down so it will fit between the frame and the clutch.
When installing GL1000 carburetors, a particular order of installation should be followed for best results. Find that method outlined here.
The GL1000 fuel pump eventually fails. As of a couple years ago new OEM replacements could still be found.
The so-called ignition ballast resistor should be permanently bypassed on every GL1000. Dealer mechanics did this routinely back in the day.
I have serviced more GL1000s than most people. Despite this, I have never encountered a riveted clutch "B" plate that had disintegrated. Such failures are talked about a lot on forums however.
Don't put an aftermarket keyswitch on your GL1000. They're really poor quality. You're better off with a good used factory one than a new aftermarket switch.
Failing fan switches are common. Part of servicing one of these bikes should always include a test to see that the fan comes on automatically when the temp gauge reads between 1/4 to 3/8 of the way into the white zone. If the temp gauge isn't working, then look for the fan to come on when the engine is almost too hot to touch. Resist putting a manual switch on the fan.
Aftermarket control cables are no bargain. They have never been as good as OEM. Unfortunately, this is virtually all that is available now.
It is well known that the 78-79 models of the GL1000 had significantly better tuning from the factory. Part of that may well be the fact that the carburetors were decreased in size thus better performing at low speeds.
Related to the above, many people may not remember that Honda positioned the inaugural 1975 GL1000 as a sportbike. Advertisements spoke of the machine in terms that seem comical and oddly inappropriate today. But that long ago big engines and disc brakes--especially two of them--were the things of the "sport" genre. This also explains why the carburetors were so large.
The Dyna S ignition system is designed in such a way that the roles of each pickup are reversed left to right from that of the original Kettering (points) ignition.
Though many view the original ignition system as difficult to maintain, aftermarket alternatives offer only one real advantage and many disadvantages. The one advantage is of course the elimination of the need of frequent readjustment.
One of the secrets known by those with significant history with this bike is that the Champion A8Y spark plug is particularly well suited to this engine. It is of course only marginally better performing than the standard NGK D8EA, but it is better.
The carburetor's pilot screws should be set to three turns out. Though slightly over-rich, this compensates for the lack of an accelerator pump.
The cam belts are best tensioned by feel combined with manual override of the tensioning springs.
A slight richnening of the carburetor's primay main jet is very effective on this bike for inproving throttle response.
When using a float level gauge care should be taken to not let the tool rest in the gasket retention notches of the carburetor body.
Exchanging the slide return springs for those from the DOHC CB750 improves low speed carburetion.
The original Kettering ignition points with proper setup will last 20,000 miles.
One of the throttle cables has a mid adjuster. Unlike the same facility in the form of the CBX1000 model's cable mid adjuster, which is welcome and needful, the one on the GL1000 has no real purpose.
Marvel Mystery Oil and Honda's Gold Wings have something of a narrative relationship. Which is really too bad. Use that stuff on your household door hinges, not anywhere near your motorcycle.
The GL1000 driveshaft has the universal joint welded on. The two are therefore replaced together.
Corrosion at the main fuse afflicts the GL1000. When you detect wiring in the area that is hot to the touch, it is starting to happen and needs to be repaired.
A floor jack and the removable frame rail make engine removal and replacement much less difficult than it otherwise might be.
The left side ignition points run the engine's front two cylinders, the right side the rear two cylinders.
Thanks to the way the carburetors are layed out, they are the easiest to synchronize of any vintage multicylnder Honda.
Incorrect cam timing is often found on the GL1000. Presumably it happens when riders replace their cam belts. The engine will run decently but the idle will be uneven and inconsistent, and unable to be fixed until the cam timing is corrected.
®