Sports Cycle

The Nature of the Beast

Motorcycles are mechanical devices. Bikes that have tried to hide their mechanical nature have usually failed to win over the motorcycling public. Philip Vincent, founder of the Vincent-HRD motorcycle company, discovered this in 1954 when he tried to sell versions of his magnificent Vincent motorcycles cloaked in fiberglass bodywork. The failure of the Black Prince and Black Knight helped seal Vincent’s fate, and the last Vincent motorcycle was constructed at Vincent’s Stevenage factory in 1955.


Subsequent fully enclosed motorcycles have fared little better than the Vincent. Ducati marketed a fully enclosed series of bikes, the Pasos and 907 I.E., in the late 1980s and early 1990s, but these never set motorcycle buyers on fire. As a result, Ducati now offers several models with small half fairings (the devices mounted at the front of a motorcycle to protect the rider from the elements) or no fairings at all to better showcase its engines. Honda tested the market for shrink-wrapped bikes when it introduced the Pacific Coast in 1989. This model did so poorly that it was withdrawn from the market; it was such a competent all-around motorcycle, though, that it rose from the dead and is now back in production.

Other designers learned from the lack of success of these bikes, and newer designs, like the recent wave of sporting twins from Japan, highlight rather than hide their engines. Motorcyclists appreciate a bike’s mechanical nature, and any biker worth his or her leather jacket is well-versed in the anatomy of a motorcycle.

Meeting the Motor

The motor seems a logical place to start when dissecting a bike. Motorcycles are, after all, named for their engines. The engine, more than anything else, gives a motorcycle its character and personality. Looks may stir you to buy a bike, but it is the characteristics of the engine that keep you riding it year after year. As Philip Vincent said, “Motorcycles are supposed to be ridden, and one cannot see the model when one is riding it” (Vincent, An Autobiography, 1976).

The engine proper is usually divided into two parts - the lower portion, called the bottom end, which includes the parts that transmit power to the rear wheel, and the upper portion, called the top end, which is where the internal-combustion process takes place. The engine also includes a system to introduce a fuel charge into the chambers where combustion takes place. This is called the induction system, and consists of either a carburetor (or more likely carburetors), or else fuel injectors, and it works in conjunction with a series of valves that are part of the engine’s top end.