Power Unit and Straddle-Type Vehicle

摘要

An engine unit includes a crank shaft that receives a driving force of an engine and a moving pulley that is movable in an axial direction. Keyholes are formed on an outer peripheral surface of the crank shaft. Axially extending guide holes are formed on a boss portion of the moving pulley in positions that correspond to the keyholes. Ends of keys are mounted to the keyholes. The guide holes receive therein bases of the keys to guide relative movements of the moving pulley and the crank shaft in an axial direction.