Abstract: An engine apparatus for an internal combustion engine which includes a first rotary valve having an indentation adapted to open an intake passage to allow air to be introduced into a combustion chamber, and a second rotary valve having an indentation to allow exhaust gas to flow from an exhaust chamber to an exhaust passageway. A first mode changer can be utilized to vary the open position of the first rotary valve, and a second mode changer can be utilized to vary the open position of the second rotary valve. A seal member can be used in lieu of either mode changer or two seal members can be used in lieu of both of the mode changers.

Abstract: A mode changer for an internal combustion engine comprises a body member disposed within a housing. The body member may be adapted to communicate with an outer surface of a rotary valve. A resilient member may be disposed in the housing capable of biasing the body member against the outer surface of the rotary valve. An engageable member may selectively move the body member. A method of changing the timing of an engine is provided. The method comprises the step of rotating an intake rotary valve having a leading edge and trailing edge for registry with an intake passage, changing the point of registry of the leading edge with the intake passage, closing the intake passage at a fixed time, rotating an exhaust rotary valve having a leading edge and trailing edge for registry with an exhaust passage, changing the point of registry of the trailing edge with the exhaust passage, and opening the exhaust passage at a fixed time.