One of the Berryman B-12 Chemtool products should work well to clean the valve. If you want to spray it out, then use B-12 Chemtool Carburetor, Choke & Throttle Body Cleaner (part #0117 or #0117C). If you want to soak it, use B-12 Chemtool Fuel System Cleaner (part #0116).