PURPOSE: To make an engine possible to start only during a braked state and to prevent an accidental start by a method wherein the rotation of a kick shaft is transmitted to the crankshaft by the operation of a brake lever only during a braked state.

CONSTITUTION: When a kick pedal 103 is pushed without operating a brake lever 108, the rotation of the kick shaft 1 is transmitted to a gear 5 but since rotation damping force due to a friction clip 7 is not given to a gear 6 engaging with a gear 5, no thrust appears in the direction of the shaft but mere slip happens. Therefore, the rotation of the kick shaft 1 is not transmitted to the crankshaft 8. If a brake mechanism 105 is braked by operating the lever 108, the clip gives rotation damping force to the gear 6 through a wire 110, a lever 111. When the kick pedal 103 is pushed under this cndition, the rotation of the kick shaft 1 is transmitted to the gears 5, 6, the gear 6 receives a thrust by the rotation damping force, moves rightward and engages with a ratchet wheel 9. Therefore, the rotation of the kick shaft 1 is transmitted to the crank shaft 8.