PURPOSE: Ensure a large output and improvement on scavenging efficiency by providing a cylinder having a scavenging port and an exhaust port opened and closed by a piston and a control unit for controlling the number of times of injection in a fuel injection valve.
CONSTITUTION: A scavenging port 3 and an exhaust port 4 opened and closed by a piston 1 are opened to a cylinder 2. A lead valve 10 is interposed in an intake path 9 connected to an intake port 8, and a throttle valve 11 is disposed at the upstream side. A control unit 15 changes over controllably the number of times of injection in a fuel injection valve 14 to once a rotation of a crankshaft 16 or once two rotations of the crankshaft 16. Thus, a sufficiently large specific power can be ensured while scavenging efficient can be improved remarkably to improve fuel consumption and reduce HC.