How do I best clean my commando gas tank

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Mar 1, 2007
Hello again. What is the best way to remove any rust or corrosion from the inside of what appears to be a usable gas tank??? I want to flush it out well also after cleaning. Any good methods??? Thanks again
A couple handfuls of nuts and bolts or better a length of chain (easier to remove), add a quart of kerosene or mineral spirits and shake and tumble thoroughly. Drain the solvent and repeat until the solvent comes out clean. Finally use a quart of MEK or acetone as a final rinse and let it dry open overnight. After draining and air drying overnight, blow it out with some compressed air to finish drying. MEK and acetone are very flammable and volatile so keep it in a well ventilated area away from ignition souces.
When you are satisfied it is clean and DRY coat it immediately with your favorite, POR-15, RedKote, or Caswell epoxy. Let it cure for at least a week before adding gasoline.
If you are saving your paint job, be careful with the MEK and acetone as they will destroy most paints.
Alternatively, take it to a local metal cleaning specialist. Make sure you talk to them about what you are doing. The tank will come back clean inside and out, but most are not used to doing motorcycle tanks and can be returned with small dings and scrapes which need to be repaired (DAMHIK). Line and prime the tank ASAP to prevent rust from reforming. This costs me $60 per tank so with the extra work to repair the little dings I usually do this only if the tank is really rusty.
If it is a really rare tank like a long range fastback or steel Interstate tank, I would consider sending it to Ross Thompson who will cut the bottom out, clean it, repair any little dings, re-weld the bottom and line the tank. It comes back better than new and will need no bondo before paint. He is truly a metal working wizard. The cost will run 500-700 dollars depending on how much metal work is needed.
What Ron said. I like to use "manifold nuts",available at any good auto parts store.They are sharp edged,and brass,so there is no chance of a spark.(I used to use sharp edged desert rocks,until one day I was skipping some across the street,and noticed the sparks kicking up! :eek: ) Also,I like to do my first couple of shakes dry,because I find that any liquid slows the momentum of the nuts,and cushions their scraping effect.

If you are planning to re-use your petcocks,remove them before commencing this procedure,and plug the threads to protect them from damage.

I avoid using sealer in my tanks,unless they are actually leaking. For tanks I have used sealer in,to stop a leak,I start putting out feelers for a replacement. However, I have an RD350 tank that I sealed up years ago,still going strong, so it's probably overkill on my part.
I just re-coated a Fastback fiberglass tank with Caswell. The inside had a de-laminating, ethanol eaten coating that was flaking off all over (could not determine what brand of coating this was, but it was coated). I used a box of 1" drywall screws which cleaned this out quite well. I then used Caswell, but I found their instructions did not quite work out for this tank. The mix comes is two tins, and the instructions state the tins are sufficent to coat two 5 gallon tanks. There is a caveat that states two 5 gallon tanks may have the same volume, but different interior areas. I found this tank needed the entire contents of both tins (though there was a bit of excess) to safely and fully coat this tank.
The solvents mentioned in previous posts will help remove the old gasoline residue, but will NOT remove the rust in a steel tank (if present). You need to do a couple of separate wash processes. One to remove residue using solvents and mechanical abrasives (nuts, bolts, etc.), then you need to repeat the process using a solvent suitable for rust removal. This is typically a phosphoric acid based material. I use Naval Jelly along with the mechanical abrasives for this step.

AttN CommandoRoadster


I like your idea of using the brass manifold nuts and will try that with my tank. Is it possible to achieve a bright metal finish inside the tank with this technique? Should I expect this to take 30 minutes or so of shaking? Or should I plan on rigging up something to spin the tank for several hours? Do I need to use a chemical rust stripper after the nuts have knocked out the loose rust flakes?

Any elaboration of this process would be appreciated.

My tank does not leak, but is has been sitting for many years and has a thin layer of rust inside.

Anyone have experience with Kreem tank kit? I am also not convinced I should do a lining step if the tank is not leaking. Anyone have input?



I used Kreem on a NOS fiberglass tank many years ago. It worked fine for me and is still in good condition. However, many have had difficulty with Kreem peeling and clogging the fuel system with used tanks.

I would use RedKote, POR-15, or Caswell's epoxy.
They say the Kreem stuff doesn't hold up to ethanol fuel. I believe it's also not rated for fibreglass tanks. I have no desire to test those claims myself!

I used Caswell on the glass tank currently on my 750. I did it a year ago and it's doing fine. They typically seem to fail after about two years though, so I guess the jury is still out on this one.

That Kuhn tank that came with my 850 has been coated with RedKote. It looks good but I don't think anyone has put fuel in it since the coating was done. I probably won't either. Look for it on ebay soon! 8)

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