Sealing structure in direct acting type auto-by starter

To prevent the entry of ambient air and liquid such as rainwater into a direct acting type auto-by starter and thereby prevent the formation of rust in the auto-by starter, by adjusting pressure fluctuations in the auto-by starter caused by the operation of a starting valve for opening and closing a starting intake passage. A starting valve is lifted to open a starting intake passage to start an internal combustion engine. Pressure in a sliding space for the starting valve is increased, so that the gas in the sliding space flows out. The flow of the gas is absorbed by an increase in volume inside a bellows boot mounted on an upper portion of the starting valve. When the starting valve is lowered by the operation of a spring member, the pressure in the sliding space is reduced to allow the gas flow from the bellows boot into the sliding space.