US Patent 7097162 Carburetor with fuel vapor control

A carburetor includes a body having a fuel and air mixing passage formed therein and an opening in fluid communication with the fuel and air mixing passage, a fuel metering assembly carried by the body and including a fuel metering diaphragm that defines at least part of a fuel chamber that is communicated with the opening, and a groove formed in the body and open to the fuel chamber. The groove communicates at one end with the opening so that fuel vapor in the groove can be moved from the fuel chamber to the fuel and air mixing passage via the groove and opening. The groove is preferably provided at least in part in a peripheral portion of the fuel chamber to guide vapor to a fuel jet as the fuel vapor moves within the fuel chamber.