Abstract: A two-cycle internal combustion engine is provided which is capable of preventing the blow-by phenomenon, thereby improving both fuel economy and exhaust purifying performance, and superior in the response of fuel injection volume. In a two-cycle internal combustion engine wherein a chamber is disposed in scavenging passages which provide communication between a crank chamber and a combustion chamber, sealable control valves are disposed in an inlet and an outlet, respectively, of the chamber. A fuel feeding system is provided for the supply of fuel into the chamber. The chamber is brought into communication with one scavenging passage out of a plurality of parallel scavenging passages. The control valve, disposed in the chamber outlet which is on the combustion chamber side and on a scavenging downstream side, is positioned at the bottom part of the scavenging passage communicating with the chamber with respect to the control valve disposed in the chamber inlet which is on the crank chamber side.

Abstract: An exhaust control device for a two-cycle engine which does not impart a change of a shape of an exhaust passage. An exhaust control device is provided in an exhaust port opening to an inner peripheral surface of a cylinder hole of a two-cycle engine wherein a cylinder wall portion adjacent to the exhaust port is formed with a rotational face obtained by rotating an arc having substantially the same curvature as the inner peripheral surface of the cylinder hole about a rotational axis C.sub.1 extending at a right angle to an axis C of the cylinder hole in the outside of the cylinder hole and a recess defined by both ends at a right angle to the rotational axis C.sub.1 and in communication with the exhaust port.