Overview
With the clutch pedal completely pressed or a motorcycle's lever pulled entirely towards you, there is no direct link between the engine and the driveshaft, so no power can pass from the engine to the driveshaft and wheels. With the pedal entirely released, there is full contact between the engine and the driveshaft, via the clutch plate, which means that the engine can apply power directly to the driveshaft. However, it is possible to have the clutch plate partially engaged, allowing the clutch to slip. As a result, only a fraction of the power from the engine reaches the driveshaft.
Read more about this topic: Clutch Control