All CBX1000's suffer from low cylinder compression. Bad valves are mostly to blame, but also this engine's 500 F degree (documented) operating heat wears out its cylinders quickly also, resulting in two to three times the as-manufactured piston-to-cylinder clearance. Just 120-130 psi compression is common, a significant loss from the factory 170 psi.
The CBX's carburetors have very tiny internal passages that gum up quickly. They also are complex enough to demand expert attention when they need it. Most people approach the carburetors with not enough intensity of focus.
Jet kits don't work on these carburetors and rebuild kits ruin them. Dynojet kits absolutely dump fuel into the engine. Any perception of this working means only that there is something very wrong with the engine, and almost assuredly this includes tight valves and abysmally low cylinder compression. A Dynojet kit is not necessary to compensate for individual "pod" air filters. That can easily be accomplished using factory parts.
Most people overtighten their drive chains and most lube them improperly as well.
Fun fact: These carburetors can evaporate most of their float bowl volume in just a few hours. It can be challenging to start the engine normally if you're not aware of this.
There are LED H4 headlight bulbs available to replace the stock Halogen one.
1980 and later models can be even more challenging to start. Their vacuum fuel shutoff valve requires engine cranking before the float bowls can refill. Reduce the strain on the starter motor and battery as well as the potential for spark plug fouling by clamping the vacuum hose during the first few seconds of cranking and waiting while the fuel flows. Give it at least five minutes. It takes a while to load up 300 milliliters of fuel.
Don't test your regulator/rectifier the way in the official manual. Test it dynamically, while it is working.
Draining the carbs is a frequent need on a CBX. In addition to running Sta-Bil full-time, if your rides are more than three weeks apart the carburetors must be drained. This is easiest if the overflow hoses are permanently removed. On the 79 model removed hoses will also prevent the infamous cylinder hydrolock.
Early model CBX's came with a plastic spacer at one end if the battery bix. Removing the spacer allows a larger battery to be used.
If still using an old-school flooded cell type battery, be sure to route your vent hose carefully. Aside from the obvious acid related damage, Honda says in a bulletin that even the hydrogen fumes coming from the hose can do damage, particularly to the drive chain.
Honda has their own version of molybdenum disulphide grease. It is the perfect thing for Pro-Link bushings, and its role as an assembly lube is borne out by its use on cam bearings.
Fun fact: Doing a leakdown test requires the valve cover to be removed because there is a top dead center (TDC) mark only for cylinders #1 and #6.
When assembling these engines you really need to have an inch-pound torque wrench.
There is a part that is found in different places on different years of the CBX--sometimes near the hesdlight, sometimes under the fuel tank. It's called on the parts diagram, "rectifier". What it is is a diode. It's part of the starter safety interlock. It prevents the neutral light from flashing on each time the clutch is pulled in. If the diode fails shorted, that's what happens, the neutral light flashes each time the clutch is pulled in. If the diode fails open, this makes the clutch have to be pulled in to start the bike, even when in neutral.
At 350 watts, the stock alternator is powerful enough and durable enough to do its job. Even the all-too common and potentially expensive issue of excessively-worn drive discs is cheaply and instantly overcome.
I use only factory oil filters. Unlike aftermarket types, they are consistently high quality.
Centerstand use is really preferred on these bikes, especially when you consider the hydrolock issue. But also unless you use the centerstand your drive chain isn't likely to get the maintenance it needs.
Fun fact:The Pro-Link model comes pre-equipped with a secondary fusebox in its fairing for the accessory gauges that were offered.
Corbin seats were once very popular on CBXs.
If installing a big bore kit or in any other way increasing cylinder compression, be sure to back off the ignition timing to compensate. This is easiest to do at idle, by retarding the timing from the stock 10 degrees to 7 degrees.
Many put on Dyna or another "high performance" set of ignition coils. The only actual advantage is that any coil will be better than one almost fifty years old. For one thing, whatever the advertised output voltage, the spark will never see more than is required at any given condition and load. This varies constantly. And, when a new coil is installed and does make a difference, the benefit is improved carburetion. Yes, carburetion. The relationship between fuel and ignition is a symbiotic one.
As with every vintage Honda, the CBX's electrical connectors are of a design whose terminals are exposed to the ravages of the elements, thus require frequent inspection and ultimate rehabilitation. The three most at risk--the alternator, main fuse and rectifier connectors--should be disassembled, the terminals cleaned or replaced, and the terminals soldered to their wires before filling the two Canon plug halves with non-metallic grease and reconnecting them.
I've rebuilt a number of transmissions on these bikes. Like any Honda, they hold up really well until you thrash them, then they get beat up "dogs", the mating parts on the sides of the gears. Transmission parts are discontinued so all replacement parts are necessarily used parts.
The valves in the CBX cannot be refaced. As with all of Honda's 1970s valves, they are plated according to Honda Service Bulletin SL84, dated May 4, 1971.
The countersunk screws in the 1979-1980 CBX's cam end covers often seize and are hard ti get out. Using the Pro-Link models' regular screws in place of the twin-shock's screws will prevent this seizure.
The brakes on almost all the CBXs I see are in need of attention. Neglect, improper servicing and poor quality rebuild parts are the usual causes.
Fun fact:The CBX is not a powerhouse, but it is seductive and surreal in its finesse, its mechanical solidness, its sound and feel.
Not known for difficult shifting, the CBX shifts best when the clutch is properly adjusted.
Save the Marvel Mystery Oil for cleaning stainless steel sinks and oiling household door hinges. Don't let it anywhere near your bike.
The valve clearances absolutely must be set at least to the end of Honda's recommended range. I go a liitle past it and find the engine really "likes" it.
Although each year of the CBX engine uses different camshafts and different carbs, they are all interchangeable. Mix and match, it doesn't matter.
Yes, the CBX like all 70s Hondas has glass fuses. Archaic, you might say. However, I don't have any problem with them. There is a fellow making a really beautifully designed blade fuse adapter for the fuse box on the top of the fork. Check it out.
The front brake discs on the twin-shock models (1979-1980) can warp pretty noticeably, resulting in brake pulsation.
Fun fact: Timing the CBX ignition requires a degree wheel. The factory sold dealers a special tiny version of a degree wheel for this. It's discontinued of course and a real degree wheel is much better anyway.
Oddly, many of the CBXs I see are missing the jam nut on the sidestand bolt.
When the CBX engine is removed and then replaced, it is not unusual for the upper left rear engine spacer to be missing.
All of these bikes have loose steering bearings. The fork should not simply flop side to side when raised off the floor.
In a recent year, two out of three CBXs in my shop had melted igniters. And unfortunately, the expensive aftermarket replacements have been proven to be poor quality.
Putting a Bosch type relay is a common mod. For the purpose of getting more volts to either the headlight or the ignition. It is far better however to repair or replace the wiring harness, the cause of the lost voltage.
The struggle to install the CBX carburetors into their rubber manifolds results in some cases of the carbs not being all the way installed, but only partway. They are fully installed when the vacuum port screws are almost touching the manifolds.
There are a lot of things people do to their bikes that they are sure improved them. In many cases however the real cause of the improvement was "unintended consequences", that is things that changed collaterally. For example, the fresh valve adjustment that accompanied the head gasket replacement.
Fun fact: Cycle Magazine, February 1978 said of the CBX, "We came to believe that in the 1047cc, 24-valve, four-overhead-camshaft CBX-six, Honda had the haymaker it wanted. The objective--to build the fastest production motorcycle available anywhere in the world--has been met. The bike is more than fast; it is magic. The exploding glitter of its technical credentials lights up the sky."
Engine heat destroys the cam chain tensioning parts, four parts altogether. These are very expensive to replace and need replacing as part of an engine rebuild.
It is important to properly install and tighten the engine hangers, some of which have to be removed for each valve adjustment, and all of which are removed each time the carburetors are. It is not unusual to find these threads stripped.
1979 models suffer from a looser than ideal fit of the cams to their middle couplers ("oldham couplers", Honda calls them). The result is a noise that sounds like very loose valve clearances. But isn't. The aftermarket offers oversize substitutes for the couplers to eliminate the noise.
Fun fact:The engineers at Honda distributed an internal (not published) memo describing the CBX's maximum engine temperature as just shy of 500 F degrees. I have measured the engine's temperature at the head's cooling fins at 350 F degrees and climbing. I have no trouble believing the 500 F, especially if it's at the spark plug. Sitting still in traffic on a hot day has the potential for heat-softening the piston rings.
The CBX engine uses Hy-Vo cam cam chains. These have a high specific density. So they're quiet when properly tensioned, but make an alarming racket when loose.
Most owners under-fill their crankcase oil. Due to the oil cooler, a warm engine has a lower level than a cold one. Checked cold, the level will be deceptively high.
On my own CBX I installed a turnsignal beeper from a Honda scooter. Just loud enough without being intrusive.
Among the few factory service bulletins on the bike is one advocating a change in the ignition centrifugal advancer. This was initiated in response to a magazine road test that was not as complimentary as hoped for.
Fun fact: Nothing is cheap on a CBX. An engine top end rebuild done professionally and correctly will probably cost more than you paid for the bike.
Many owners have gone to the trouble of installing the slightly higher-lift 79 cams in their later models. I did it too. But it's hard to say there was any advantage. Plus, the later models are known for wider powerbands and more seamless tractability.
The air-assisted rear shock on the Pro-Link models (1981-1982) can be tuned somewhat by varying the oil level, which changes the amount the air pocket in the shock is compressed. In fact, the shock came from Honda with too little oil. Adding oil with the shock still in place (using a syringe) can eliminate bottoming of the shock.
Don't use non-OEM valve cover gaskets and bolt seals. Their inferior rubber material overcompresses and leads to oil leaks. The factory ones are still available.
It is not true that the cam bearings ("caps") from one CBX head can't properly be used on another one. It can and has been for as long as these bikes have been with us.
Don't hamner your carburetors into the manifolds. I see some every year that have been damaged in this way.
Fun fact: The online voltmeter is not a reliable indicator of battery condition because it is wired some distance from the battery. The voltmeter should be considered an alternator brush wear indicator.
The camshaft bearing bolt torque is incorrectly listed in the official manual, leading to seized and broken bolts. Use an inch-pound torque wrench and torque to 80 inch-pounds.
Using ratchet straps or some other desperate measure when installing the carburetors into their manifolds can cause distortion of the choke linkage.
Some people who have split the CBX engine cases have disturbed the primary shaft "clocking" and found, engine back in the frame, the ignition timing then way off. I have seen primary shafts with desperation-drive notches filed into the shaft to compensate.
Another place I've witnessed the evidence of angst is in rubber intake manifolds that someone has reamed out to make the carbs go in easier.
At factory Honda tech school it was suggested that to get brighter instrument illumination the slightly higher wattage bulb from the Turbo model's parking light could be used.
Aftermarket keyswitches are very poor quality. If you need a switch, find a good used factory one.
Fun facts: The engine does not have be lowered to get the valve cover off, the later model's fairing does not have to come off to remove the valve cover, and the exhaust does not have be removed to remove the carburetors.
There is a factory bulletin on cylinder base gasket oil leaks.
It was at Honda school that I learned to blueprint the CBX accelerator pump.
Avoid aftermarket suppressive plug wires. They lack electrical conductivity, for one thing.
Avoid "premium" gas. Hondas from this era will carbon up quickly if premium gas is used.
When a corporate Honda employee I rode a company loaner 1982 model and when I left the company I had a used 1981 I purchased at employee auction.
Exhaust bluing is most often caused by not monitoring the engine idle during warmup.
Hazard flashers are easy to add to a bike. Just three parts are needed: A universal handlebar switch, a 552 flasher, and two diodes.
Fun fact: Very few aftermarket exhausts for the CBX require the carburetors to be rejetted. Changes to the air intake however can necessitate a ten main jet size increase.
Big bore pistons do not cause the carbs to need rejetting. Increased compression automatically richens carburetion.
Running the carbs "dry" does not prevent them from varnishing up. That's a myth. The float bowls will not be emptied and the carbs' intricate passages will still retain fuel.
Fun fact: Adjusting the cam chains is best done statically with the valve cover off.
Synchronizing the CBX carburetors is not intuitive. It helps to have a lot of experience. Even career mechanics find it challenging.
It is not necessary to have six vacuum gauges when synchronizing the carburetors. The official manual shows just four gauges being used. With goid technique this works well and the only advantage to six gauges is speed.
The CBX's fast idle mechanism is almost always in need of adjustment. It's a fairly crude and somewhat unintuitive mechanism.
Aftermarket control cables are very poor quality. Unfortunately, this late in time they are almost all we have.
The Denso alternator conversion is not a bad thing, but neither is it the correct answer to an alternator needing service.
Fun fact:Shinko tires work good on the CBX.
In more than fifty years as a nechanic, I was there disassembling these engines at the very beginning, have serviced countless numbers of CBXs, and have rebuilt almost a dozen CBX engines in just the last ten years.
Full metallic brake pads noticeably improve the bike's brakes.
As with any vintage Honda, silicone brake fluid is the only sensible thing to use on a bike that sees so little use.
Aftermarket gaskets and gasket sets are not the best quality.
The best pistons for this bike are available from Wiseco as kit #CK138. These are not in the catalog and were believed to have originally been commissioned by Bill Brint. They are light, correctly shaped, and fit in the cylinder with almost cast part precision.
When installing big bore CBX pistons the 3mm increase comes so close to the cylinder studs that Honda's excellent ring compressors will not work.
Fun fact:The CBX throttle is easily modified for a faster turn ratio.
The crankcase recirculation solids distill box ("spuge box") needs to be emptied periodically. Failure to do so will increase the contaminants that enter the carburetors. I see the results of this constantly in the carburetors I rebuild.
Handlebar switches and wiring harnesses are available on the aftermarket.
Installing the CBX's choke cable intuitively will result in idling issues. You have to outhink the design for it to work correctly.
Many of the batteries available for the CBX fit incorrectly in the battery box. Specifically, the shorter battery height results in a dangerous positioning of the positive battery cable close to the steel battery box's side.
The clutch is misadjusted on every CBX I have encountered. Proper adjustment is done at the pressure plate, not at the cable.
The front brake lever is oddly shaped. I always reshape it to match the shape of the clutch lever.
Gap your NGK D8EA spark plugs to 0.032". Works great.
The carburetor overflow hoses are what caused the hydrolock issue. This was confirmed by American Honda. On a 79 model remove them.
Aftermarket 6-1 exhausts are a poor choice for this bike. They are necessarily restrictive. And one particular 6-1 introduces rogue wave pulses in the engine that result in performance glitches that are solved only by replacing the exhaust.
This bike's charging system of course does not charge the battery at an engine idle rpm. This is not a defect however. It is a holdover from Honda's 1970s electromagnet alternator designs on the early inline fours. The CBX alternator is fairly high-powered. Until the GL1200 emerged in 1984, the CBX's alternator was the most powerful in all of Honda's motorcycle lineup.
Ironically, most CBX owners are satisfied with very mediocre engine performance resulting from lack of proper maintenace.
Fun fact:The CBX does not have great fuel economy because it has six carburetors. But more than that because its engine runs so hot. The CBX is a liquid-cooled engine. That liquid is gasoline.
Out of the CBX's six spark plug caps, half are usually in need of replacement on any given bike, and all require tightening.
Dynatech never made an ignition for the CBX. The one they offer was actually designed for a different bike altogether. Because if this, it needs to be modified when installed or the result will be almost 10 degrees of ignition timing overadvance. Not what you want on an engine that is already the hottest-running 70s Honda.
Fun fact: The CBX's ignition system Honda calls Transistorized Pointless Ignition, or TPI. It is simply transistorized Kettering. It does not offer any performance advantage over point ignition. The US government forced powersports manufacturers to go electronic at the advent of emissions laws for the first time affecting motorcycles in 1978.
The 1981-1982 Pro-Link model engines have different valves than the 1979-1980 models. The valves' margins are thicker.
The noise that is often called "clutch rattle" is really primary chain rattle. Although hydraulicly tensioned, poor engine tune can produce the noise. A worn clutch basket can add to this if course.
This engine's spark plug holes are often cross-threaded.
The CBX has 24 valves. The engine's heat causes the valve seats to shift in place, requiring very careful machining to correct. Shim type valve train practice is to "tip" each valve to keep its clearance adjustment spec high in the available shim range. The stock valves cannot be tipped so high quality stainless steel valves should be used. This and the high degree of very special and very skilled work make the CBX valve job a $3000 proposition. That's with the head in-hand.
The factory specified maintenance intervals are spaced just 3700 miles apart. Today's owners can't quite fathom this.
You can find many of the Honda service bulletins relating specifically to the CBX on online forums.
Fun fact:The first edition of the factory service manual contained an error in cam installation that changed the engine's firing order and thereby resulted in over-stress breakage of the cam chain. A memo (not a bulletin) regarding this problem was sent to dealers, but otherwise it was not publicized. This error is possible because the cams install right side first then left, with a slot joining the two sides.
Because they are positioned close to the rotor's edge and thus endure high speeds, the alternator brushes need replacement frequently.
Starting a CBX whose battery has discharged through disuse of the bike can cause burnout of the ignition "spark units" (igniters).
Starting problems can often be traced to a bad neutral light switch. The switch and light are part of the starter safety interlock. The switch's resistance can decrease power to the starter.
The official manual says little about carburetor rebuilding and even less about carburetor synchronization.
The manual is not a very good resource on servicing the 1981-1982 models' Pro-Link shock. Perhaps this is because the shock was not designed to be rebuilt.
The replacement main oil seal for the Pro-Link shock has been discontinued for a score of years.
A service memo sent to dealers warned that the tach drive gear must be removed before attempting to remove the valve cover. A number of cam bearings (the drive doubles as a cam bearing) have been damaged by folks not being aware of this. Back in the day, American Honda had Honda Japan supply them with replacement bearings to send at dealer request.
The originally-available valve adjusting tool was discontined almost immediately and replaced with a different tool that looked very much like the one Kawasaki was using. The earlier tool could result in bent valves when used incorrectly.
The 1981-1982 models have a rear shock low air pressure warning light on the instrument panel.
Honda is long out of the valve shims. However, several sources have taken up the slack. There are even cars that use the same shim. So they are plentiful.
The CBX valve shims are not quite what the manual depicts. Instead of 0.05mm increments, they are actually made in 0.02mm steps. For this reason, the use of a micrometer is mandatory. A caliper is not accurate enough.
Honda has begun reproducing the preferred valve adjusting tool. It is a far better choice than the ubiquitous fishhook type aftermarket tool. Among the drawbacks of the aftermarket tool is that it offers no provision for fully seating the shim on its replacement as the factory tool does.
Factory valves and valve guides are all gone now. The aftermarket substitutes do not inspire as to their quality. The same is true of pistons and piston rings, with the exception noted above.
The CBX cylinder does not need an aggressive crosshatch finish. The ethos of the very noticeable crosshatch is very old-school, obsolete.
Enlarging the intake ports of this engine is very misguided. The ports and valves are already too large from the factory. You will only slow intake air even more, leading to detonation and other issues.
Fun fact:Fitting individual K&N air filters has the potential, when accompanied by a big bore, of increasing this engine's horsepower by at least 25hp, and actually closer to 40hp with good tuning.
At one time, Dynojet sold their own K&N individual air filter kit for the CBX that consisted of five pieces (the middle two carbs shared a filter). Two different editions of this kit existed. Both are discontinued.
The CBX doesn't need an aftermarket exhaust, and due to the engine's camming none will appreciably increae its power. And of course reasons to put on an aftermarket exhaust are personal, as is the choice of exhaust. However, in my view the very best that was available was the Supertrapp 6-2. All stainless steel, and with tunable baffles and one of the best fit and construction in the industry.
Changing from the stock cartridge air filter element to a K&N replacement will affect carburetion. Even more if the airbox lid is removed.
Fun fact: Most American CBX riders overuse their rear brake. Honda anticipated this. They revealed to the European press that they made the rear disc oversize to suit the American market.
The 1981-1982 pleated paper air filer element is higher quality and longer lasting than the 1979-1980 models'. There are at least two quality, "knockoff" aftermarket sources for the later filter.
Kibblewhite is not the only source for stainless steel valves for the CBX but has proven to be the highest quality source. Unfortunately, every handful of years the company inexplicably stops making them for a time.
The best (and only viable) carburetor rebuild "kit" is the Randakk kit. It isn't a kit in the traditional sense. It does not include any metering parts or float valves. And that's a good thing as that is what's wrong with kits. The Randakk kit consists of o-rings, diaphragms and screws.
The intake manifolds (rubber "insulators") can pose some difficulty. Even brand new (Honda still sells them), the carb-to-manifold geometry is such that insertion of the carbs requires quite a lot of stretching of the rubber. They aftermarket ones aren't as pliable. New or old, stock or aftermarket, a heat gun helps a lot.
The alternator's drive discs are a legend. Defectively made at the factory, they self-destruct in short order. There are a few different solutions, but I believe the best is to defeat them. Shim them until they cannot slip, ever.
Honda sold its float valves only with the seats. This made them very expensive. Kawasaki used the same Keihin parts, including the float valve needles, and sells them without the seat. It is not necessary to replace the float valve seat unless someone has modified it. I always use Keihin float valves in CBX carbs. The aftermarket ones are very poor quality.
Fun fact: A big bore kit in this engine significantly reshapes the powerband, making the bike much more tractable and more enjoyable at low speeds.
The 1979-1980 front brake master cylinder reservior had a steel insert that supported the rubber bellows. If this part is not put back during a rebuild the reservior will leak.
In winter conditions the engine oil may thicken up and the engine's starter clutch (sprag) malfunction.
On the 81 model I owned for almost 50,000 miles, I exchanged the stock saddlebags for those from the GL500 Silverwing. Same shape, same abs/aluminum construction, but 4 inches deeper and a different mounting system that was easy to adapt. These were on the bike I rode from San Diego to Illinois and back in 1985.
Honda, through its Hondaline accessory division, offered many add-on accessories for the CBX. These included a kit to convert the US models to Euro spec handlebar/controls ergonomics, a turnsignal relocation kit for the faired Pro-Link models, altimeters, clocks, engine guards and more.
Back in the day, many riders opted to replace the Pro-Link bike's windscreen with the taller one from the later VF750S and VF1100S Hondaline sport fairings.
At one time there was an aftermarket kit to convert the Comstar wheels to wire spoke wheels.
Fun fact: The CBX horns are adjustable. This adjustability is for compensating for internal corrosion that might make them inoperable.
The Pro-Link bikes have plastic and steel bushings in their progressive shock linkage that require periodic lubrication. The swingarm must be removed for this.
Late in 1978 some California Honda dealers were invited to a hotel for an annual new model training seminar. We were introduced to the CBX then. And it was amazing. Just prior, the salespeople at the dealership in which I was a mechanic reported some buzz they were getting about an all-new, ultra-performance Honda model. The CBX made quite a stir at its introduction.
Almost my first sight of a CBX was also in 1978 when one with a hole in the crankcase was wheeled into the shop. Thus was our introduction to the hydrolock issue and subsequent several crankcase replacements on customers' bikes.
Squealing disc brakes on a CBX are easy to remedy. Paper gaskets behind the pad works best.
The first year CBX had a 630 size drive chain, a really big chain. No one knows why. Subsequent years had the smaller 530 chain.