How to remove rust from a motorcycle gas tank

One of the perks of being able to work on motorcycles is that you can generally find them fairly cheaply if work is required on them. Typically a bike that needs repairs has sat for a while, usually with an empty tank. This means that rust has built up over time, as was the case with a 1981 Honda CB650 that I acquired. To say this thing contained rust was an understatement; it had rust spots. Luckily, however, the tank had no pinhole leaks or anything and was completely solid. Now for the fun part! I will explain the process of removing rust from a motorcycle gas tank. As I said, this was done on an 81″ CB650 so it’s tailored for that, but I’m sure it will work on most other bikes.

What you will need:

  • acetone
  • Distilled water (it is important that you only use distilled water)
  • two-stroke oil
  • A 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: DO NOT MIX ACETONE AND RUBBER! If you use rubber to seal the fuel exit, replace it every time you drain the acetone mixture as the acetone will eat it up.

At this point, I’m assuming you’ve removed the gas tank from the bike and that it’s empty. Here is a step by step.

  1. Plug the fuel outlet and make sure it is tight
  2. Fill the tank about half full with acetone and let it sit, turning it occasionally
  3. wait overnight
  4. Shake the tank and empty the acetone/rust mixture into a bucket
  5. Fill the tank halfway again with acetone and this time drop the chain in
  6. Shake the tank often and vigorously. The chain knocks off any remaining rust
  7. Empty the acetone/rust mixture into the bucket
  8. Fill the tank with distilled water and empty it. Do this until only fairly clean water comes out and no more rust is heard. I put a hair dryer in the tank hole and dried it immediately afterwards
  9. Fill the tank about ¼ full with 2-stroke oil and shake it around, then drain it
  10. Please dispose of the acetone and other nasty chemicals properly

I highly recommend installing an in-line fuel filter in the fuel line between the tank and the carburetor. It filters out all small particles and keeps 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 carburetor a good clean.

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