Patent ID: 8371972

Claim:
A power unit comprising: a power source; a rotating shaft that receives a driving force output from the power source, the rotating shaft including a crank pin; and a moving pulley including a cylindrical-shaped boss portion extending in an axial direction of and fitted onto the rotating shaft to be movable in the axial direction, wherein two shaft side holes are formed on an outer peripheral surface of the rotating shaft, two boss side holes are formed on and extend through the boss portion in positions that correspond to the shaft side holes, two detent members are inserted through the shaft side and boss side holes, wherein one end of each detent member is within either one of the shaft side holes or one of the boss side holes, and another end of each detent member is received by the shaft side hole or boss side hole that corresponds to the shaft side hole or boss side hole that the one end of the respective detent member is mounted to, the corresponding shaft side hole or boss side hole that receives the respective detent member comprising a slot extending in the axial direction to guide relative movements of the moving pulley and the rotating shaft in the axial direction, further wherein a first straight line extends through an axis of the rotating shaft and the detent members and a second straight line extends through the axis of the rotating shaft and a center of the crank pin, a first of the detent members being positioned so that an angle between the first straight line and the second straight line is at least 45° and at most 90°, the first detent member being arranged on a first side of the rotating shaft and the second of the detent members being arranged on a second side of the rotating shaft opposite the first side, the axis of the rotating shaft being between the first detent member and the second detent member.