How to clean and seal a fuel tank
So, you just got a great deal on a fuel tank on eBay, and now you want to get it ready to go on your motorcycle. Whether it’s a brand-new tank or a crusty relic, you’ll want to properly clean and line it before you even consider what color you are going to paint it. Sealing the tank is cheap insurance against a fuel leak, which at the least could ruin an expensive paint job and at the worst cause a fire. When choosing a sealer brand, always make sure to check that it is impervious to ethanol fuels. Unless you plan on always carrying your own fuel with you, chances are you’ll eventually end up filling your tank with an ethanol blend. Many tank sealers can be dissolved in ethanol, and, as you can imagine, running dissolved tank sealer through your carburetor or fuel injection leads to a variety of problems.
The process of cleaning and sealing your tank is easy but time consuming. You’ll want to make sure you set aside enough time to complete the job, as some steps may require an hour or more to complete and cannot be stopped once they are started. For this article I will be using the tank clean and seal system from KBS Coatings. Since you will be using chemicals, make sure that you are working in a well-ventilated space and are wearing gloves and eye protection.
Remove all gas caps, petcocks, and fuel fittings from your tank. Plug the resulting holes and any vent holes with threaded plugs or rubber stoppers. Whatever type of plug you decide to use, make sure the result is a watertight seal.
Remove the plug from the filler neck and drop about two dozen sheet metal screws inside the tank, and then replace the filler neck plug and shake vigorously for five minutes. Rotate the tank while shaking it to ensure that the screws encounter all the interior surfaces of the tank.
Dump the contents of the tank onto a clean paper towel and note the amount of rust particles removed during Step 2. Repeat Steps 2 and 3 until you no longer see rust particles on the paper towel.
Double-check that all holes are securely plugged, and then immerse the entire tank in warm water for 10 minutes. Slowly rotate the tank, looking for air bubbles, which indicate leaks. Most tank sealers can only seal pinhole-sized leaks, so any large leaks found during this process should be welded/soldered before continuing.
Mix KBS Klean 1:1 with hot water. Remove the filler neck plug and pour the mixture into the tank.
Replace the filler neck plug and shake the tank vigorously for five to 10 minutes (longer for heavy soil), rotating the tank to make sure that the degreaser touches all interior surfaces. Immediately move on to the next step.
Rinse the tank thoroughly with warm water. It’s important not to let the degreaser dry inside the tank.
Pour one pint of KBS Rust Blast into the tank.
Replace the filler neck plug and slosh the Rust Blast around in the tank, rotating the tank to ensure that the rust remover touches all interior surfaces. Repeat this step every five minutes for a minimum of 30 minutes to ensure that the interior of the tank stays wet.
Thoroughly rinse the tank out with warm water.
Allow the interior of the tank to dry completely. Expedite the process by using a small fan or eat gun to blow air through the tank while all the plugs are removed.
Stir the can of KBS tank sealer thoroughly and pour the entire contents into the tank.
Replace the filler neck plug and rotate the tank to ensure that the sealer touches all interior surfaces of the tank.
Pour out the excess sealer.
Remove plugs and rotate the tank a 1/4 turn every two minutes for the next one to two hours while the sealer is setting to keep it evenly spread throughout the tank. Allow the tank to cure for 96 hours before refilling it with fuel.