Fiberglass tank repair

Does anyone recommend a fix for a fiberglass fuel tank that that is leaking from the bottom rear of both sides. I suspect the previous owner who had always used race fuel added a splash of pump gas to start the bike just before I bought it. Not knowing this the splash of pump fuel (likely with ethanol in it) sat in the tank for about 2 weeks before I noticed that it was leaking. I'm hoping a simple coating will do the trick but I don't know what brand to buy.

The product I recommend is from www.caswellplating.com I heard about it from a plastic engineer It is a 2 part epoxy that is imperious to many harsher chemicals. Products that rely on solvent evaporation have a limited lifespan in an ethanol based fuel base.

I would recommend doing any fiberglass repairs first any use the Caswell to seal and bind the structure of the tank. I have a tank from a 1972 Bultaco Alpina that has a serious delamination problem. Be sure to follow preparation and applications instructions fully from Caswell. Caswell had a bad rap on this forum from a member that violated the instructions by pouring the treatment from the first tank into a second tank thinking he was going to get 2 tanks done instead of one. Bad choice. The product started to tack over in the first tank so it was already kicked over when poured into the second tank. Not the fault of the instructions as they point out to never try to reuse it. If you want to do something with the leftover, plan ahead and cast something with it.

I have not had good results with Caswell in my Penton tanks, as a matter of fact I have 6 worthless tanks now because of failed Caswell. All the tanks were meticulously prepped before the Caswell was applied and every possible precaution was taken. The product just does not work IMO, or more accurately, it will not work unless the surface can be prepped like any other fiberglass repair, which cant be done without cutting the tanks apart. Believe it or not I have heard more than once of people with ethanol damaged tanks just letting them "air out" and they regain their integrity. In the case of my tanks I think the only thing I can do is cut them apart and sand/prep them and put a real coat of epoxy on them.

I've been letting the tank air out with a small fan aimed at the filler neck and after 3 days the soft tack spot where the leaks were have hardened up. I can look in the tank while holding it up to the light and the inner coating is gone in the leak spots but in tact and thin on the rest of the surface.

Since you don't recommend Caswell what brand of coating do you prefer?

I dont recommend any, they all have the same problem, which is that you can not properly prepare the surface inside the tank unless you cut it open. Its not a problem with Caswell itself, I'm sure it is excellent on a prepped surface, but in 3-5 years it will start peeling off in sheets if you use it as advertised.

I never use pump gas, the previous owner is the one who put pump gas in it just before I bought it. He offered to buy me a new tank but I'm going to try fixing it first. The maker of the tank recommended I use Caswell so I'm going to give it a try. If I get 3-5 years out of it I'll be very happy since it's on a flat track race bike it will likely get a makeover before it gives out.

I'll let you guys know how it goes.

Have had nothing but good results with Caswell. A friend I work with has done several Penton and Spanish tanks without any problems, and several have been in use for well over 5 years. Overkill on the prep is the key. I use sheet rock screws (count them so the same number comes out as goes in) and shake up the tank to scratch up the interior, and then rinse and rinse and rinse. Then put the sheet rock screws back in and start over.

You can not rough up the inside too much. If I had access to a paint shaker I would give my Cota tank a ride on that with the acetone and sheet rock screw mixture. You should be able to look inside the tank with a penlight to check the progress. I will just have to shake and rotate myself. Then I have a 1987 Jaguar XJS HE convertible that has the split fuel tanks that allow the top to fold down below the body lines. In 1989 Jaguar resorted to having a single tank and a protruding top hump as a result. The Hess and Eisenhart fuel tank system system is infamous for vapor leaks. Hopefully someone finds a low pressure Rochester valve to cure that.