An apparatus useful in a two-stroke cycle engine or in a pump as a piston disposed within a piston cylinder. The piston cylinder has an intermediate piston cylinder head disposed transversely across the interior of the piston cylinder. The piston has a lower portion and at least one upright extension member extending upwardly from the lower portion. The upright extension member extends upwardly into the upper portion of the piston cylinder through a gap between the intermediate piston cylinder head and the piston cylinder wall. A piston top wall is disposed transversely to the piston cylinder side wall and is attached to the upper portion of the upright extension member of the piston. An upper piston cylinder chamber is defined above the piston top wall. An intermediate piston cylinder chamber is defined immediately below the piston top wall and a piston cylinder lower chamber is defined below the intermediate piston cylinder head.