Removing fuel and rust from a gas tank

I’m working on a 1982 nighthawk 450. I have the tank off and drained but there is still a little remaining gas and rusty debris in the tank. How do I get this last little bit of fuel and rust out? (it wont dump out of the cap or the valve) Any info would be appreciated. Thanks.

The method I use is kind of brute force, but works pretty well. I remove the petcock from the tank then I put a few handfuls of spare nuts, bolts, and washers into the tank and shake it around to remove all the rust from the inside. As long as everything fits into the petcock whole, you’ll be able to get it all back out. Works great!

Electrolysis is another technique that works phenomenally well. My buddy just cleaned out a couple tanks, I’ll see if I can get some photos of the process from him. It’s a bit time consuming, but completely destroys all rust inside the tank. Works like magic.

Notes from a Reader:

I would suggest removing the tank from the bike then remove the fuel peacock. Once the peacock is out you can slosh the tank around and get the rest out. I would then get some kind of liquid cleaner (I use Simple Green Degreaser) and mix it up in a pail (or utillity sink) and fill, shake, empty, repeat until you have all the crap out of the tank.

Here in Canada we have a product called “Evaporust” avaliable at Canadian Tire that is in a liquid form. I put it in the tank (fuel peacock reinstalled and turned to “off”) and let it sit for at least 12 hours, then I flip the tank over and let it sit 12 more. I then remove peacock again and drain it all out and tape a shopvac to the holes for the fuel peacock and turn it on(with gas cap removed). I let the vacum pull air through the tank for 15 to 20 minutes and check to see if all the moisture has been pulled out of the tank.

Home Depot sells a simular product by Zep that can be diluted with water or put straight in as well if you cannot find Evaporust.

Be sure to clean the screen on the fuel peacock as well while you have it out.

Evan Fell

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