Two-cycle recompression internal-combustion engines having a cylinder closed at both ends and a piston reciprocating therein, such piston performing at the same time the functions of both a working piston and a piston for the pump which supplies a fresh charge to the engine, one end of the cylinder and the corresponding end of the piston constituting the working cylinder and piston, while the other or rear end of the piston and the corresponding end of the cylinder form a pump for introducing a new charge into the working end of the cylinder. In engines in this subclass the supply or exhaust ports, or both, are generally formed in the cylinder-wall and are then controlled by the piston as it reciprocates, the piston forming a closure for such ports when it is required that they be kept closed.
