How to Clean the Interior Coating of a Motorcycle Tank

Remove varnish and sludge from your motorcycle's gas tank.

Modern motorcycle fuel tank interiors are chemically treated to coat the interior of the fuel tank and protect it from water and the effects of gasoline additives. Gasoline that has soured or evaporated produces a varnish on the inside of the tank. This varnish can peel off and clog the filter on the fuel petcock. Two-stroke engines that burn premixed oil and fuel may produce sludge in the tank that can cause persistent fuel filter clogging. Once drained and removed from the bike, clean the tank’s interior to remove sludge and varnish.

Things You'll Need

• Rubber plugs and caps
• Liquid dish detergent
• Water

Instructions

1. Remove the fuel petcock from the tank.

2. Plug the holes in the fuel tank -- to include the tank vent, petcock hole and crossover tube nipples -- using rubber caps, plugs or short sections of hose plugged with bolts or golf tees.

3. Mix a strong water and soap solution using dish detergent. Fill the tank about half full with the solution through the fuel filler cap and install the cap.

4. Vigorously shake the fuel tank in all directions. Invert the tank while shaking to ensure all areas of the tank are thoroughly agitated and washed. Drain the solution through the fuel petcock hole. Repeat this step as required to clean the tank.

5. Flush the tank with clean water until all traces of soap have been removed. Remove all of the plugs from the tank and allow it to dry fully before installing the tank and adding fuel.

Tips & Warnings

• Use a soap that dilutes oil. Liquid dish soaps that contain grease-cutting agents are suitable.

• Tanks that are rusted or have damage to the interior coating must be cleaned and re-coated. There are several commercial cleaning and coating products available. Contact your motorcycle dealership for advice on brands of commercial cleaning and coating products.

• Do not use carburetor cleaner inside of the fuel tank as it can damage the tank coating.

• Perform this procedure in a well-ventilated area. Do not smoke or allow open flames in the area while performing this procedure.

• Exercise caution if using a commercial cleaning agent. The agents are caustic and destroy the painted finish on the tank. Always closely follow the manufacturer’s recommendations when using a commercial cleaner.

References

• 2009 Softail Models Service Manual; Harley-Davidson Motor Company