Charon
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Shaft drives are usually thought to be less efficient, because of the two 90-degree direction changes required. One at the front, from the transverse engine and transmission to the drive shaft, and one at the back from the longitudinal drive shaft to the rear wheel. Bikes with longitudinal crankshafts and transmissions, such as BMW, Moto Guzzi, Gold Wings, and others have only one directional change so lose less efficiency.
Shaft drive bikes have another quirk called "shaft jacking." When power is applied the rear of the bike tends to rise, or "jack." When power is cut, the rear tends to squat. With chain or belt drive, power application tends to make the rear squat. The problem is more noticeable with higher power. Either system can be so engineered as to eliminate the effects, but the suspension becomes more intricate and costly. It seems a minor point, but consider the case when one is leaned over in a corner and parts start to drag. Reducing the power by closing the throttle is one of the natural reactions. With a chain the rear tends to rise, and the dragging is reduced. With a shaft reducing the power makes the rear drop and actually makes the dragging worse.
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