PURPOSE: To contrive effective use of a self-starting motor after starting in such a way that a self-starting motor is coupled to the engine, through a clutch and further it is coupled to the air pump through a clutch which works in the reverse direction.

CONSTITUTION: A one-way clutch 3 is fixed to one end of a self-starting motor 1, while it is also interlocked to the engine 5, through a gear 4 and a crankshaft 6 to start the engine 5. Besides, a one-way clutch 7 which makes operation in the reverse direction to the clutch 3 is fixed to the other end of a motor 1, and further the clutch 7 is interlocked to an air pump 8 through a gear 9. In consequece, revolution of the motor 1 is transmitted only to the engine 5, at the time of starting, and transmitted only to the air pump 8 after starting.