Closing the choke plate when starting a cold engine restricts the air entering the carburetor through the air cleaner and creates an increase in suction on the jets. This increase in suction causes more fuel to be drawn into the engine and provides a richer mixture necessary for starting a cold engine. As soon as the engine starts to operate, the spring-loaded poppet valve located within the choke plate opens to prevent over-choking. As the engine warms, the choke must be opened manually to the wide open positions.