Challenger, Champ, Colt and Sapporo

The main reed valve is actuated by diaphragm movement, caused by pressure pulsations generated by piston motion in No. 3 cylinder crankcase (sealed by a seal cover). A small hole in the seal cover discharges engine oil and blow-by gas. The sub reed valve is actuated by exhaust vacuum generated from pulsations in the exhaust system between front and rear catalytic converters.