Long ago, so we are constantly reminded by people like Bob Currie, motorcycles were infinitely rebuildable, limited in their potential lifespan only by the willingness of their owner to rip out worn bits and substitute them with universally available spares. It was unheard of for a manufacturer to cease making spares for a model, and any spotty oik could fathom the secrets of the simple and straightforward construction.
Balls, I hear you mutter, but it has to be admitted that there’s more than a little truth in it one has only to compare even recent examples of British machinery to the most simple and straightforward Japanese bikes to understand something of vital importance to the secondhand buyer: design means nothing outside the context of an engineering environment.
What does this mean? Let’s look at two typical machines. First, a 1955 Coventry Thunderflash - 650cc vertical twin, iron barrels, iron frame, you know the kind of stuff. They were made in enormous quantities and the engine was a development of an earlier 500cc engine with many common parts, whilst chassis parts are interchangeable. The electrical system was so basic that the voltage regulator from an Austin 7 worked. All the parts that are easily damaged are readily available because they are shared with other manufacturers.
The 1987 Yamaki 600 single, however, is a different kettle of fish. Despite its superficially simple spec - only one cylinder - it might as well be an RE5 for all the interchangeability it offers. Machines like this have no common spares with others outside their brand, and precious few inside it. The 600 is totally different in most respects to last year's 550 and has little connection with even earlier versions.
The electrical system is so complex that most auto electricians refuse to work on it, and the large number of sealed units mean that even the gifted amateur stands no chance. The battery is tailored exactly to the machine, the CDI likewise; drop it, and you'll find that only Yamaki levers fit the pivot bodies, only Yamaki indicators have the same lenses... does it all sound familiar?
The reason for this depressing state of affairs is the engineering environment in Japan. This is universally market geared, designers are given no constraints to work within as the weight of promotion and the state of the market, coupled with the availability of cheap finance and the rise in disposable income of the average buyer in the last twenty years guarantee that this years model will sell like hot cakes as long as it’s a bit faster or tricker than last years. There is currently no reason at all to build durable motorcycles, let alone establish standards within the industry for certain components.
You can’t blame the Japs for doing this - they are in business to make money, something the British never really admitted, but if you’re planning to buy a used bike with a view to doing it up, it’s essential to understand this fundamental attitude, and realise that bikes are built to thrill not last, these days.
So where does this leave the buyer? Well, there are certain machines which boast better levels of interchangeability than others, and it’s a good idea to find out which ones they are. All BMWs have a high level, but the cost of new parts are breathtaking, though there are specialist BMW breakers. Triumph, BSA, Enfield et al all use Lucas, Delco and Dunlop bits, and the majority of their accessories can be interchanged. Even exotica like Guzzi and Laverda use bits by Bosch, Hella and others. All of these firms publish catalogues for the auto electrical trade, and your local auto electrician may be able to supply many bits at a lot lower cost.
Amongst the Japs, late 70’s Yams had a certain number of bits that fitted other Yams, but major accessories were still all different. It’s interesting to note that one of the best bikes for replacement bits is the new Matchless as it’s more or less made up from a collection of bits out of the parts catalogues. Part of the problem with used Japs is that in trying to keep them going beyond a certain time, you are doing something they weren't designed for - and you can expect no help from the factory. It may be worth paying a bit extra for a higher quality European bike that can be refitted ad infinitum with used bits or substitutes.
Paul Callomon
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