Sports Cycle

The Power Transmitter: Motorcycle Clutch

One of the major obstacles designers of early motorcycles faced was creating a system for engaging and disengaging the power transmitted to the back wheel. This wasn’t a problem as long as you were moving, but once you decided to stop, it quickly became important.

Most early motorcycles used a leather belt to transmit power from the engine to the rear wheel. This belt connected directly to the crankshaft. To give the rider some control over the flow of power, a pulley mounted on a lever was used to tighten the belt. This system proved to be marginally effective, even on the underpowered machines of the time, and it soon became clear that a better system was needed. That system was the clutch. The clutch is a series of springloaded plates that, when pressed together, transmit power from the crankshaft to the transmission.



Early clutches were operated by a foot pedal, like on an automobile, with levers mounted to the gas tank to shift gears in the transmission. This setup proved to be cumbersome and awkward. When the British began exporting motorcycles to the United States with handoperated clutches and foot-operated shifters, U.S. riders soon realized the benefits of such a system, forcing Harley-Davidson to adopt hand clutches and foot shifts for its motorcycles.

Nearly every full-sized motorcycle built since World War I uses a clutch, with a couple of notable exceptions. Honda experimented with a clutchless, or automatic, transmission on its CB 750 in the mid-1970s, then repeated with their Dual-Clutch Transmission (DCT) on VFR1200F, and Moto Guzzi marketed an automatic bike at about the same time. Neither was a sales success. Unless you run across an example of one of these rare bikes, you should probably resign yourself to learning to use a clutch.