A-B1691944-AI SHAFT-THROTTLEOne New Aftermarket Replacement Throttle Shaft Fits Briggs & Fits Stratton Small Engines This throttle shaft is a carburetor component Fits Briggs & Fits Stratton (B&S) small engines commonly found in lawn mowers, riding tractors, generators, and other lawn and garden power equipment. Seated inside the carburetor body, the throttle shaft controls the butterfly plate that regulates airflow and fuel mixture entering the engine, governing engine speed