Allow me to guess why you’re wondering how to clean rust out of a motorcycle gas tank.
You’re tired of cleaning or replacing fuel filters, taking your carburetor apart, or swapping injectors? Are you trying to get an older bike back on the road, but don’t want to (or can’t) buy a new fuel tank? If so, you’re probably looking for a solution. Well, you’ve come to the right place!
I’ve been there, more than once over the years. Your service manual probably won’t tell you much about how to deal with a rusted fuel tank. Mine never did. At best, you get “If rusty, replace.” Well, there’s definitely another way!
How to Clean a Fuel Tank:
- Assess & Plan
- Prepare
- Execute
- Rinse
- Dry
- Seal
Clean Rust Out of a Motorcycle Gas Tank – Assess & Create a Plan
What options you have for removing rust inside your motorcycle’s gas tank is influenced by the gas tank itself. Every gas tank is a little different in it’s level of corrosion. Some (like the one pictured) are still in pretty good shape, and the rust is just starting to form. I’ve seen others that looked like the USS Arizona.
Remove your tank from the motorcycle, remove the fuel pump module (if EFI) or Petcock (if carbureted), the gas cap, and anything else you can. You’ll want to order new gaskets for these things ahead of time. When it comes time to actually clean rust out of a motorcycle gas tank, you’ll be putting things inside the tank to help agitate the rust, so start thinking about what will best fit in the provided holes, and how you’ll remove it later. (I tend to prefer using a handful of nuts and bolts, *steel* bb’s, a bunch of wood screws, or a length of dog chain depending on the tank. Removal is usually easiest with a telescoping magnet like this one.)
In order to keep everything *inside* the tank, you’ll want to use an assortment of plugs, stoppers, and probably some combination of tapes to plug all the holes you made by removing everything. Plugs, stoppers, and corks work well for circular holes. Oddly shaped holes (like for your fuel pump module) may require the use of your old gasket, plus a block-off plate. You can make one out of a piece of sheet metal pretty quickly.
Prepare
Once you have an idea what your plan of attack looks like, take a minute to make sure you have everything ready:
- Agitator – A bunch of nuts/bolts, wood screws, steel bbs, or a length of dog chain work well for this. They’re going in the tank with the rust remover to help scrub the rust off the walls. Which one you pick will depend on the size of the holes in your tank, the number of cracks and crevice’s (small items like the BBs are better at getting in tight spaces, but the larger stuff offers more scrubbing power).
- Rust Remover – Evaporust (available here, or at your local o’reilly’s) is my favorite thing to use, but if you’re on a tighter budget, white vinegar works too. I don’t recommend using anything stronger, as the stronger chemicals can actually damage paint, eat through the tank, etc. Get enough to fill your tank 1/3-1/2 way. If your tank is particularly rusty, get twice that amount. You’ll still put the same amount in the tank, but the chemical will probably get weak partway through. When you notice the rust isn’t dissolving as fast, you’ll need to dump it out and replenish.
- Tank is sealed off – your plugs, tape, block off plates, etc. are all installed and firmly in place.
- You have a tank liner ready to go – I strongly recommend using Caswell, Inc’s Epoxy Gas Tank Sealer to re-line your tank once you’re done removing the rust. It’s more chemical resistant than the other brands. It’s also not effected by ethanol, and has much better bond strength than single component products. Basically, it will ensure that your tank is rust-free for life.
Execute
Add your agitator and rust remover to the tank, seal up that last hole, and shake gently as long as you can. When you’re good and tired, set the tank down. Go drink a beer or 2, and come back! Rotate the tank a bit, then repeat this process until you’ve covered the whole tank all the way ’round. Check on the progress of your tank every few rotations. Keep going until you see nothing but nice, bare metal inside.
Rinse
When the inside of your tank is good and rust-free, get ready to rinse. Start with putting the biggest stock pot you have on the stove, full of water and get it hot. It shouldn’t be boiling, but it should be too hot to touch comfortably. More on this in a bit.
While your water heats up, dump the rust remover out, and remove your agitator of choice. Pull off all of the plugs, block off plates, etc. and run your garden hose through the tank to wash any remaining chemicals & sediment away.
Put your plugs and block off plates in place again. If you used vinegar as your rust remover, add a few drops of dish soap to your tank. Now *carefully* pour in your hot water, and shake your tank around a bit more. The hot water will transfer the heat to the tank walls, which will speed up the drying process.
Now pull off all your plugs and dump the tank out one more time.
Dry
While the tank is still hot, you’ll want to get warm air flowing through it. Cheap hair dryer works best, but a heat gun can be used on the lowest setting as well. Careful though, many heat guns get hot enough to damage the paint. Basically the goal is to dry the tank as quickly as possible without getting it too hot. If you don’t work quickly enough, or the humidity is high, you’ll see little spots of surface rust start to appear. This is called “flash rust”, and it’s exactly what we’re trying to avoid. A little is OK, but a lot means starting over.
Seal
If you’re using a sealer, be sure to follow the instructions that came with it EXACTLY! You don’t want to have to do this whole thing again any time soon, so making sure the tank is prepped is key. A little extra time on the prep work will save you from having the sealer bubble, peel, or flake off later.
If you’re not using a commercial gas tank sealer, I recommend using a bit of 2-stroke oil or kerosene to coat the inside of the tank and prevent that flash rust we talked about earlier. Then you can go about putting it all back together and refilling it with gas so you can go for a ride!
