® Ten things every Honda CBX owner should know

The Honda CBX is a very special motorcycle. At over 40 years old it is far from the fastest or best performing. Even at its debut it enjoyed king-of-the-hill quarter-mile status only until the Suzuki knocked it off its tenuous throne merely a few months later. Heck, with its origin in a 1950s NSU design its multivalve multi-cam engine was already old tech before it was even produced. So no one has illusions, not then and certainly not now. And heavy? And wide? And a 19-inch front wheel? But with all those antiquated characteristics, there is still an allure, a captivating finesse, special character, and visceral thrill that is rare and hardly matched in today's motorbike offerings. I especially appreciate the CBX engine's unique DNA, a sort of amalgamation of vintage European technological brashness with practical, durable Japanese engineering. It's very much a Lamborghini with Asian foster parents. It's a neat bike, very possibly my all-time favorite, both to own and ride as well as to service and rebuild. However, in this day of low-maintenance vehicles this attention-demanding machine is an anachronism, a thing unexpected and unfamiliar. And all too often, sadly neglected. Thus I find the following things important enough to encourage every CBX owner to put them on a list of things to know.

1 First, and this really is first. The number one shortcoming found in any used CBX is cylinder compression. And it matters. This is in fact the CBX's achilles heel, it's downfall. Often this is due to cylinder wear and compromises made during assembly at the factory. But even more often it is due to valve issues. Because Honda used soft valves in the CBX, even very low mile engines have already lost a certain percentage of their compression. It is practically an axiom that 120-130 psi is observable in any example of the CBX one will encounter, roughly a thirty percent loss from the as-manufactured 170. Every machine. Ones with only 7,000 miles on them suffer the effects, and valve wear is extreme by just 15,000-miles. And all because of cheap valves, for which quality long-lasting aftermarket replacements are available and strongly recommended. And what I use. You really don't know what you're missing if you haven't ridden a properly running CBX.

2  Second, the state of the brakes on every CBX that enters my shop is inevitably disappointing. But they needn't be. While typical Honda 70-80s tech, meaning single-action, collet design as in virtually every mass-produced passenger car and thus relatively low-performance, the little-known truth is, the stock brakes -- that is, with almost all stock parts -- can actually be phenomenal. All it takes is a little knowledgable attention. I spend nearly as much time on the brakes as I do the engine on every CBX I fettle, with the biggest problem being improper assembly and the use of really bad aftermarket parts. High performance brakes aren't the answer. Getting after the brakes you already have is.

4  Third, the CBX alternator has got a bad rap. It's not a pile, contrary to what many believe. Once set up properly, it, like the brakes, is trouble-free and a good performer. There is nothing wrong with the Kawasaki-based alternator conversions. They're fine. But they are completely unnecessary. 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 disks is easily and cheaply overcome.

5  Fourth, the ignition system. First, the Dyna ignition systems available for the CBX are a good product, but one that is usually incorrectly installed. You really don't want to ride an already hot running CBX around with its ignition overadvanced by 10 degrees. Second, the transistor boxes, or "igniters" as many call them, are all going bad. In a recent year, two out of three CBXs in my shop had melted igniters.

6  Fifth, stay away from jet kits. They are bandaid fixes even on those machines for which they are relatively suitable. That is, they make up for other issues on those machines that should themselves be addressed. But on the CBX, they are all the bad and more. Criminal, is the word that comes to mind. Don't ruin your CBX carburetors with a Dynojet kit.

7  Sixth, with the engine a stressed member of the frame, it is important to properly install and tighten the engine hangers, parts which have to be removed for each valve adjustment. Almost every CBX that makes its way to me has had someone install them incorrectly -- often stripping the threads in the frame -- or tighten them in the wrong order, which also promotes damage. What's worse is aftermarket hangers. I have yet to see one that is made correctly. Really, you ask? Yes. What aftermarket hanger makers fail to do is to replicate the stock hanger's offset. The original main engine hangers have an offset between the top and the bottom. All the aftermarket ones I have worked with are absent the offset, requiring shimming the bottom with washers to properly create it, which I have had to do many times. Failing to do so results in the hangers being bolted up crooked.

8  Seventh, with the CBX's carburetors being as fiddly and old-school as they are, and having circuits that are really tiny and precise, they are prone to varnishing up very easily. You simply must keep Sta-Bil fuel stabilizer in them at all times, round the clock. Unless you think nothing of having them expensively rebuilt each riding season. Sta-Bil really works. Use it. And by the way, ethanol has nothing whatever to do with this.

9  Eighth, as with every vintage bike, the CBX's electrical connectors are of a design whose terminals are exposed to the ravages of the elements, thus requiring frequent inspection and ultimate rehabilitation. Expect corrosion and melting of the plugs. The good news is, all the needed parts are available, even from Honda, and getting after this has the potential of improving electrical performance. Done right the repair will never have to be done a second time. And it really needs doing.

9  Ninth, due to the CBX's hot-running engine, on warm days the carburetor's float bowls can evaporate as much as half their volume in just a few hours of sitting after a long ride. Be aware of this when starting the bike later, as it means the carburetor bowls have to refill before the engine will start. It is not good practice to simply wail away on the starter hoping the bike will eventually start.

10  Tenth and last, on 80 and later models the above issue is exacerbated by the vacuum fuel shutoff valve which will not allow fuel to flow until the engine is cranking over during starting. So even more time needs to be allowed. You can reduce the strain on 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 (use a hemosat), then turning off the key and waiting while the fuel flows on its own into the float bowls. Give it at least five minutes. It takes a while to load up 300 milliliters of fuel.

I hope this has been instructive and useful. The CBX is a wonderful bike. I had mine for over 50,000 miles. But I have actually discouraged more than one individual from acquiring one when I felt they would be challenged by the inevitable needs previously-owned machines tend to have due to neglect and ignorance. If you are a new owner, or are about to be, see my article on the costliness of putting a used CBX in shape after purchasing.

 
Further reading:
The challenging Honda CBX

Last updated January 2022
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