Reed valve definition
A one-way valve used in a two-cycle engine . It is made of a flat strip of metal that lies on the floor of the crankcase over a hole connected to the carburetor . As the piston moves up, the vacuum developed in the crankcase lifts the reed valve off the hole. The vacuum causes the fuel-air mixture to flow from the carburetor into the crankcase . Then, as the piston starts to move down, pressure increases in the crankcase pushing the reed valve down, closing the hole and sealing the crankcase .