Abstract: A method is provided for converting a conventional four stroke internal combustion engine having four cylinders into a two stroke engine. The camshaft assembly including the camshaft having cams thereon and the drive assembly which couples the camshaft to the crankshaft are replaced with a modified camshaft assembly such that the inlet and exhaust valves are each opened once per revolution of the camshaft. The resulting two stroke engine includes two pairs of pistons, each pair of pistons having a first and second piston which are fired synchronously. The pairs of pistons being spaced 180 degrees apart such that two pistons are fired synchronously for every half rotation of the crankshaft.

Abstract: A two-stroke engine includes an intake-and-scavenge valve in the cylinder head together with a fuel injection system, a recirculating type pressure lubricating system, and a blower or turbo charger assisting in charging the cylinder with air and also assisting in scavenging the exhaust gases . The piston head is domed with one side curving downwardly towards the exhaust port formed through the wall of the cylinder above the bottom dead center position of the piston head. The exhaust port slopes outwardly and downwardly following generally the slope of the piston to facilitate the flow of exhaust gases therethrough assisted by the scavenging air entering through the inlet-and-scavenger valve. The valve is operated by a cam mounted on a cam shaft upon the cylinder head which in turn is operatively connected to the crankshaft. The width of the cam lobe is such that the opening, closing and duration of opening of the valve is controlled with the valve being opened approximately 140.degree.