Exhaust timing controller for two-stroke cycle engine

Abstract

An exhaust timing controller for a two-stroke cycle engine includes an exhaust timing control valve for changing a height of an open edge portion on a top dead center side of an exhaust port opening to an inside wall surface of a cylinder bore in the engine. The exhaust timing control valve moves axially of the cylinder bore by power from an actuator and the exhaust timing is accelerated in response to rotational frequency rises in the engine. The power of the actuator is transformed into an elevating stroke of the exhaust timing control valve by the eccentric motion of an eccentric cam. A slider mechanism for transferring an eccentric motion of the eccentric cam to the exhaust timing control valve is provided between the eccentric cam and the exhaust timing valve. A straightening member extends smoothly from a portion of the exhaust timing control valve, which retracts into the exhaust port, on the downstream side of the exhaust port. An upstream side end portion of the straightening member pivots on the exhaust timing control valve. A downstream side end portion of the straightening member slidably and pivotally engages with an inside wall portion of the exhaust port.