PURPOSE: To enable easy change-over to 2-cycle operation or 4-cycle operation in accordance with the revolution of an engine, by causing a rotary sleeve in close contact with a cylindrical surface of a cylinder to rotate by mutual attraction/repulsion force between the sleeve and magnetic fluxes of permanent magnets.

CONSTITUTION: A rotary sleeve 2 has an intake window 21 capable of opening an intake port 15 provided at a lower portion of a cylinder 1, and has a plurality of rotation-drive permanent magnets 22 disposed therearound at equal intervals, and is adapted to rotate in close contact with the surface of the cylinder 1. In this case, the rotary sleeve 2 is rotated by mutual attraction/ repulsion force between the sleeve and magnetic fluxes of the permanent magnets. And the rotary sleeve 2 is positionally controlled to a position at which the intake window 21 and the intake port 21 are out of coincidence when the piston is in the proximity of a bottom dead center during a 4-cycle operation, thereby causing both elements 21 and 15 to communicate with each other with an intake timing during a 2-cycle operation. This enables the engine to be easily change over to 2-cycle operation or 4-cycle operation in accordance with the engine revolution.