MTFCA Forum

I have had great success with the POR tank treatment kit. The initial clean out involved a couple of kilos of roofing TEK screws and a concrete mixer. The screws went in the tank, and the tank went in the mixer. This gives a mechanical clean out rather than chemical. The resultant surface is squeeky clean and somewhat abraded for a good bond for the kit components.

Allan from down under.

I have had great success with the POR tank treatment kit. The initial clean out involved a couple of kilos of roofing TEK screws and a concrete mixer. The screws went in the tank, and the tank went in the mixer. This gives a mechanical clean out rather than chemical. The resultant surface is squeeky clean and somewhat abraded for a good bond for the kit components.

Allan from down under.

If its mostly varnish/shellac, the solvent for it is denatured alcohol. I have poured in a gallon and kept turning the tank over and over for
about 10days. It also helps to shake it in between turning it.
After it loosened everything up I used a pressure washer inside it to get it clean.
Unfortunatly the lovely State of California has now banned denatured alcohol for sale. I'm glad I have a stash of the stuff.

I had a problem with my motorcycle tank, crud and rust buildup.

I used to containers (about 5 ounces) of citric acid, cost, about US$10.00 with hot water, filled the motorcycle tank and left it in the sun in the afternoon and then overnight.

I poured out the result next day (it's ecologically harmless) and what a brown sludge it was. The tank was clean and shiny inside, even the nether regions only seen with a probe camera.

No further treatment was required as a BSA Bantam motor cycle is a two stroke needing 5% oil mixture, proof against further rust.

Bob - why not contact Kevin Prus & purchase a new round tank & be done with the monkey-motion ?

I thought Kevin was just making the oval tanks. I bought one from him last year.

I have both round 13-20 and oval available
Kevin Prus

We used a couple gallons of vinegar and some rocks for cleaning in stage 1.
After cleaning, rinsing it out we used the POR method.

Jugster wrote: ↑

Mon Jun 02, 2025 8:52 pm

I’m dealing with a clogged and varnished-up gas tank. The few local establishments that clean and coat gas tanks charge about $600.00 which, to me, feels awfully pricey. Is there a do-it-yourself bottle of magic chemical that I can pour into the tank, agitate the tank, pour the magic chemical out and consider the tank sufficiently clean?

The recommendations of cleaning are for different needs.
Your request for for "varnished tank" not "rusted tank".

PUR-15 Metal Prep, Evaporust, White (Cleaning) Vinegar, etc are for rust removal
Chemicals that are known to dissolve gas tank varnish ( White (Cleaning) Vinegar, denatured alcohol, Acetone, MEK, Sea Foam etc)

The you need to dispose of the residue safely.... Cleaning time + effort + safe disposal only to find that the tank had a rust hole that was sealed by the varnish... then you'll buy a new tank.

If denatured alcohol works so well, why not purchase a couple of gallons of E-85 fuel (55-85% alcohol). Slosh it around inside for a few days. It should work as well and is way cheaper than denatured alcohol at the store.

I can think of hundreds of reasons to solder up a rust hole in an otherwise clean tank, most of them being Dollars. One of the tanks I treated to a POR kit had a couple of pin holes. POR said they would be sealed by their process. I took no chances and soldered them anyway.

Allan from down under.