PURPOSE: To obtain a high output over the entire operational range of a two-cycle engine in which the valve opening and closing timing of a rotary valve is matched to the low-speed operation of the engine, by raising the charging efficiency by forming subsidiary intake ports on both sides of a main intake port, and providing check valves permitting only the flow of air-fuel mixture into subsidiary intake passages so that air-fuel mixture is drawn not only from the main intake port but also from the two subsidiary intake ports at the time of high- speed operation of the engine.

CONSTITUTION: Subsidiary intake ports 9a, 9a are formed in a rotary valve 9 in the manner that they are communicated with a subsidiary intake passage 9 extending on both sides of a main intake passage 7, so that the two subsidiary intake ports 9a, 9a are communicated with each other. The subsidiary intake passage 9 is communicated with the main intake passage 7 via reed valves 10, 10. These reed valves 10 serve as check valves. That is, they permit the flow of air-fuel mixture from the side of the intake passage 7 to the side of the subsidiary intake passage 9 by causing elastic deformation but they do not permit the opposite flow of mixture. By employing such an intake apparatus, intake time and intake area corresponding to the sum of the area of the main intake port and the subsidiary intake ports can be obtained, so that the charging efficiency can be raised over the entire operational range of the engine from the low-speed operation to the high-speed operation of the same.