PURPOSE: To prevent water from being sucked into a motor chamber and a switch chamber and also rain water from entering them without providing any water draining undercover.

CONSTITUTION: A motor chamber A is communicated with a starter outer part through a long ventilating route comprising a motor chamber ventilating hole B, a wall recessed space F, a communicating hole, a wall recessed space F, a communicating hole, a clutch chamber E, and a bent ventilating hole G. Also a switch chamber C is communicated with the starter outer part through a long ventilating route comprising a switch chamber ventilating hole D, the clutch chamber E, and the bent ventilating hole G. Thus any water is not sucked into the motor chamber A and switch chamber C by negative pressures in the motor chamber A and switch chamber C, and also rain water is prevented from entering them.