Xi 'an motorcycle driver's license is registered in the North Branch of Xi 'an Vehicle Management Office. The following is an introduction to motorcycle: 1. Working principle: when stepping on the pedal, the mechanism will press the spring, so that the periphery of the spring will tilt up and the pressing skin will be separated from the friction plate. At this time, there is no connection between the friction plate and the flywheel. Even if the engine continues to run, power will not be transmitted to the gearbox and wheels. At this time, the driver can shift gears and stop without turning off the engine. 2. Power transmission: When the crankshaft speed is low, the two friction plates can't contact the shell, so the power can't be transmitted. When the crankshaft rotates at high speed, due to the centrifugal force, the friction plate is thrown out and touches the shell, so that power can be transmitted.