Stratified scavenging carburetor

A stratified scavenging carburetor (1) with a lost motion coupling (29) permits limited relative movement of a throttle valve (2) relative to an air valve (10) so that initial opening of the throttle valve (2) off idle does not open the air valve (10) to avoid diluting with scavenging air the fuel and air mixture delivered to an engine. Rotation of the throttle valve (2) beyond a predetermined amount from idle causes a corresponding opening of the air valve (10) to provide scavenging air to the engine. Closing a choke valve (12) engages a lock lever (20) with the throttle valve (2) to move the throttle valve (2) off idle to a start position without opening the air valve (10). In another embodiment, closing the choke valve (12) prevents the air valve (10) from opening even if the throttle valve (2) is moved beyond where the throttle valve (2) would cause the air valve (10) to open if the choke valve (12) were open. Thus, a richer than normal fuel and air mixture can be supplied to the engine during a choke-assisted start and warm-up of the engine.