What should you clean a rusty gas tank out (does not leak, just rusty inside)?

[Guest]

Have a tank that had water in gas and started rusting inside.

[Nessism]

There are hundreds of postings in the archives about derusting tanks, many of them by me.

There are all kinds of different solutions to derust: Evaporust, vinegar, Kleenstrip Metal Prep (phosphoric acid), muratic acid, and even using a reverse plating methodology involving a battery and electrode. My preferred method is phosphoric acid. It works quickly and doesn't need to be neutralized, just rinsed. Key thing is to fab up some good plugs for your tank after you remove the petcock, sending unit and gas cap. After rinsing be fast with some alcohol in the tank and WD-40 to ward off flash rusting.

Good luck

[geol]

The inside of your tank will have rust because it is plain steel. Moisture in the tank over time occurs when there is not much fuel in the tank and surface rust happens. Phosphoric acid should be diluted with water I think and then it will turn the rust into an inert compound that is often used to paint over directly. If there is SCALE, then that must be dealt with by putting clean gravel or a bunch of nuts and bolts or something of the sort and shaking the tank while turning it over to break the stuff up and then treat with phosphoric acid solution. If you don't do anything with the tank for awhile, you might want to WD40 the inside but if you plan on using right away, rinse with water; dry thoroughly with compressed air and fill it all the way up with gas. Do make sure you get the water out as your bike doesn't burn a lot of water very gracefully.