A-B1691739-AI PLUG-WELCHOne New Aftermarket Replacement Welch Plug Fits Briggs & Fits Stratton Small Engines This carburetor welch plug (also called a soft plug or expansion plug) seals internal passages in the carburetor body left over from machining. Welch plugs are small, disc shaped metal plugs pressed firmly into place to prevent fuel and air leaks, maintain proper fuel mixture, and ensure consistent engine performance. Replacing a damaged or leaking welch plug is a