How to Remove Rust From a Motorcycle Gas Tank

One of the benefits of being to able to work on motorcycles is that you can generally find them pretty cheap when work on them is required. Typically, a bike that needs work has been sitting for a while, usually with the tank empty. This means over time that rust has taken over, as was the case with a 1981 Honda CB650 that I had acquired. To say that this thing had rust in it was an understatement; it had chunks of rust. Luckily though, the tank had no pin hole leaks or anything and was completely solid. Now to the fun part! I will explain the process of removing rust from a motorcycle gas tank. As I stated, this was done on a 81′ CB650, so it’s tailored to that, but I’m sure it’ll work on most other bikes.

What you’ll need:

  • Acetone
  • Distilled water (it’s important that you only use distilled water)
  • Two stroke oil
  • A length of chain 4 to 6 feet long
  • Rags
  • Something to plug the fuel outlet (I used a small piece of hose a small rag and a piece of black tape)

IMPORTANT NOTE: ACETONE AND RUBBER DO NOT MIX! If you use rubber to seal the fuel output replace it every time you drain the acetone mix as the acetone will eat away at it.

At this point I’m going to assume that you have the gas tank off the bike and that it’s empty. Here is a step by step.

  1. Plug the fuel output and make sure it is sealed
  2. Fill the tank about ½ full of acetone and let it sit turning occasionally
  3. Wait overnight
  4. Shake the tank and empty the acetone/rust mixture into a bucket
  5. Fill the tank ½ way again with acetone and this time drop the chain in
  6. Shake the tank often and vigorously. The chain will knock remaining rust off
  7. Empty the acetone/rust mixture into the bucket
  8. Fill the tank up with distilled water and empty it out. Do this until only fairly clean water comes out and no rust can be heard rattling around. I put a hairdryer in the fuel hole and dried it out immediately after
  9. Fill the tank about ¼ with two stroke oil and shake it around then empty it
  10. Please dispose of the acetone and other nasty chemicals properly

I highly suggest installing an inline fuel filter on the fuel line in between the tank and carburetor. It will filter out any small particles and keep them out of the fuel system. This system worked for me, my CB650 ran like a dream after cleaning the tank like this! The next step is to give the carb a good cleaning.