Berryman B-12 Chemtool Fuel System Cleaner (part #0116) can be used to remove gum buildup from a gas tank. If the gas tank can be removed, you’ll want to pour the product in and either let it soak or swirl it around and then drain it. Repeat until the B-12 comes out clear and colorless. If the gas tank is still installed, you might try spraying Berryman B-12 Chemtool Carburetor, Choke & Throttle Body Cleaner (part #0117) over as much of the inside of the gas tank as possible. Again, you’ll need to drain the tank and repeat until the B-12 comes out clear and colorless. Your carburetor will need a little attention, too. Once the gas tank is clean, try running 1 oz/gallon of B-12 Chemtool Total Fuel System Clean-Up (part #2616) through it. That will help clean up the fuel pump, fuel lines, carburetor, intake valves, and combustion chambers. Please be aware that all three of the products mentioned are very aggressive toward not only gum but also paint. If you’re concerned about the finish of the gas tank or any other parts of the bike, you will need to exercise extreme caution when working with B-12 Chemtool products. Good luck!