Abstract: A gas transfer port system for a cylinder of a two stroke internal combustion engine; said cylinder provided with a fixed separator plate dividing said cylinder into an upper section and a lower section; a piston in said cylinder reciprocating between said separator plate and a cylinder head; and wherein an annular skirt descending from said separator plate forms at least a portion of an annular well between said skirt and an internal surface of said cylinder; said well sealed at the bottom such that said cylinder is isolated from a crankcase of said engine; said gas transfer port system including at least one long gas transfer port connecting a lower portion of said annular well with a gas transfer port outlet aperture in a wall of said cylinder.

Abstract: A two-stroke, internal combustion engine which includes at least one set of paired first and second cylinders. The engine includes an air or air/fuel mixture inlet conduit bifurcated into inlet passages extending to respective first and second inlet ports of the first and second cylinders. A valve controls the passage of air or air/fuel mixture into the inlet passages. In one embodiment of the engine, a bypass passage provided with a bypass valve extends between the inlet ports of the paired cylinders.

Abstract: A gas transfer port system for a cylinder of a two stroke internal combustion engine; said cylinder provided with a fixed separator plate dividing said cylinder into an upper section and a lower section; a piston in said cylinder reciprocating between said separator plate and a cylinder head; and wherein an annular skirt descending from said separator plate forms at least a portion of an annular well between said skirt and an internal surface of said cylinder; said well sealed at the bottom such that said cylinder is isolated from a crankcase of said engine; said gas transfer port system including at least one long gas transfer port connecting a lower portion of said annular well with a gas transfer port outlet aperture in a wall of said cylinder.