US Patent 7261281 Carburetor

A carburetor including a mixture channel and an air channel that are separated from one another, wherein a fuel opening opens into the mixture channel. A throttle element is rotatable about an axis of rotation that extends transverse of the direction of flow in the mixture channel and in the air channel and extends through both channels. As a function of its position, the throttle element throttles a flow cross-section of the mixture channel and the air channel. The flow cross-section of a portion of the mixture channel and/or of the air channel has a non-circular shape in the vicinity of the throttle element.