| 摘要 |
PROBLEM TO BE SOLVED: To smoothly switch a motive power by carrying out a motive power- switching by a selective engagement of a centrifugal clutch by a shift means and an output adjusting means. SOLUTION: When an operator releases a throttle lever 24 and shifts a shift lever 40 from a first shift position 40a to a second shift position 40b and a driving shaft 16 is axially moved to a position P2 through a shift fork 40d, a shoe member 28 of a centrifugal clutch mechanism 32 is aligned with a cylindrical portion 38c of a drum portion 38 in a moving space S. When the operator grasps the throttle lever 24, an output of an internal combustion engine 2 is increased. When a rotation speed of the driving shaft 16 is raised to become a predetermined revolution number or more, the shoe member 28 is radially and outwardly moved in resistant to an urging force of a return spring by a centrifugal force to friction-engage with an inner periphery of the cylindrical portion 38c. Thereby, a motive power is transmitted to an output pulley 14 through the drum portion 38, a driving gear 48 and a driven gear 50 and a speed is reduced from a high speed to a low speed and a rotation driving is carried out.
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