Abstract: A four-cycle internal combustion engine having a crankshaft, a spark plug with a central electrode and a piston cylinder with an internal surface. An intake opening and an exhaust opening are formed in the internal surface. A sleeve is rotatably disposed adjacent the internal surface. A port is formed within the sleeve and is configured and positioned to sequentially coincide with the intake opening and the exhaust opening. The piston reciprocates within the sleeve and overlaps the port at the top dead center position of the piston. Conical gears on the bottom of the sleeve and on the crankshaft rotate the sleeve at one half the speed of the crankshaft to realize the four cycles of the engine.