Valve assembly using pressurized medium for controlling operating conditions of a two-stroke engine

Abstract From the Canadian patent

A valve assembly located adjacent the cylinder structure of a two-stroke engine including a valve piston, a diaphragm and a restricting member. The valve assembly is adapted to vary the height of the exhaust port of this type of engine by moving a restricting member, located in a guide channel communicating with the exhaust port, from a full-flow height position to a restrictive height position (and vice versa) . The force necessary to actuate the restricting member is a pressurized medium or a vacuum. A solenoid valve controls the pressurized medium or vacuum delivery to the valve assembly according to the engine speed N and throttle opening for optimum efficiency.