While cranking the engine, spray Berryman B-12 Chemtool Carburetor, Choke & Throttle Body Cleaner (part #0117) directly into the carburetor in short bursts—you don’t want to spray too much all at once or you’ll risk hydrolocking the engine. If you can clean out enough gum, varnish, etc. so that it runs, you should then run a high-quality fuel additive, such as Berryman B-12 Chemtool Total Fuel System Clean-Up (part #2616) to finish the job. 2616 is our strongest gasoline fuel additive, combining strong solvent technology with high-performance detergency to thoroughly clean up the gas tank, fuel pump, carburetor (or injectors, where applicable), intake valves, and combustion chambers. Good luck!