Maybe you scored a rad old tank at a swap meet or maybe your trusty steed is showing its age. But the problem of motorcycle gas tanks getting rusty is a tale as old as motorcycling itself. Much like old cars, old tanks seem to have a character to them that newer gas tanks just don’t have anymore making them that much more desirable to save and re-purpose on a build of some sort. I personally tend to collect them up in the garage and inevitably use them on a build of some sort or donate them to a friend's build.

But before we get into how to save your favorite old gas tank you should make sure it's worth saving. Some tanks could be rusted through or have such severe damage it’s probably best to pass on the rehab and make them garage art. With that being said, if you have the right set of fab skills you could save just about any tank. But that’s not what we’re talking about here. For this particular exercise we’re going to concentrate on how to save tanks that have the common surface-style rust and corrosion inside the tank that needs to be fixed to prevent sludge from entering your carb or stop further degradation of the tank. So a quick inspection of the tank should reveal the extent of the damage. Does the rust penetrate through the tank causing potential leaks? Are there cracks in the seams or welds? Once you have determined if the tank is salvageable then we can move on to the rescue.

So now we can start the rust removal process. Right off the bat I'd plan on replacing the petcock and gas cap as part of the restoration. Partially because if the tank is in rough shape then so are they and partially because this next part could potentially damage the petcock and gas cap. You're going to need about two feet of dog chain, nothing heavy duty, just the lightweight twisted chain you can buy at the hardware store for a few bucks. The next thing you are going to need is a couple gallons of apple cider vinegar. Depending on how big your tank is you may need more or less, basically I like to be able to fill the tank up about 3/4 of the way full.

Old motorcycle gas tanks are cool and have character, but you're going to need to determine whether it is salvageable or not. 

To start, close the petcock, pour in about a quart of the apple cider vinegar and drop in that dog chain. Put the cap back on, fire up some of your favorite workout music and get to shaking. Give it a rather violent shake for a few minutes turning it over and over in different directions. Open the cap and dump out any large flakes you may have knocked loose. With a flashlight make a quick visual inspection, if you can see anymore loose pieces that may come of with a good beating pour some more in the tank and shake it again for a few minutes. Once you've taken out all your pent up aggression by shaking the crap out of the tank retrieve your chain from the tank through the gas cap. If you have trouble with this a magnet is your friend. I'd like to take a minute here to address some garbage info I've seen floating around the interwebs- DON'T USE GRAVEL OR LOOSE NUTS AND BOLTS. I have seen people recommend using things like gravel and loose hardware, but unless you have a few spare hours to kill trying to get tiny bolts and bits of gravel out of your tank, stick with the chain, it'll save you a ton of time.

The next part is much less labor intensive. Fill up the tank (at least 3/4 full) with the apple cider vinegar and let it sit for at least 24 hours. Two days is better if you have the time, and periodically give it a swishing around. You don't have to shake it like before, just roll it around. After your 48 hour soaking simply dump out all the nasty fluid. To ensure the tank gets good and clean and to neutralize the vinegar you need to do one last step. Take a gallon of distilled water, add about a half a box of baking soda to it and flush out the tank really good. At this point it's a good idea to hit the inside of the tank with some compressed air to speed up the drying of the tank.

At this point the tank should be in really good shape but it's in danger of flash rusting because it's a raw metal surface. At this point I highly recommend sealing the tank with a tank sealer kit to prevent flash rust and keep the inside of the tank in good shape for years to come. This is also the best time to replace the petcock and gas cap. More than likely if the tank is in bad shape, so are they. Overall it's a pretty easy process, take your time and go work on those motorcycles.

Here's the condensed, step-by-step instructions.

How to Clean Rust Out of Your Motorcycle Gas Tank

  1. Score a cool old motorcycle gas tank. Swap meets rock!
  2. Inspect the tank to determine whether it's salvageable.
  3. Buy about two feet of dog chain. Yes, dog chain.
  4. Buy a couple gallons of apple cider.
  5. Close the petcock.
  6. Pour about a quart of the apple cider vinegar into the tank.
  7. Tighten gas cap.
  8. Shake tank like you're making James Bond a martini (a few minutes at least).
  9. Open up gas cap and pour out any large flakes.
  10. Repeat Steps 6-9.
  11. Fill tank about 3/4 full with apple cider vinegar and let sit 24-48 hours.
  12. Swish liquid periodically.
  13. Dump out.
  14. Take a gallon of distilled water, add about a half a box of baking soda to it and flush out the tank really good.
  15. Dump out water/baking soda mixture, dry with compressed air.
  16. Seal with a tank sealer kit.
  17. Bonus step - replace old petcock and gas cap because they're probably just as shot as the old tank.