How do you make a fiberglass gas tank? I rmember about 15 years ago I tried to repair an old Honda 3 wheeler gas tank with fiberglass but eventually the gas ate through the fiberglass and it leaked agian. I've seen a lot of boats with fiberglass gas tanks so I know there is a way to do it, but how?

You should be able to buy tank sealer at pep boys or somewhere similar to that. it comes in a plastic bottle full of white shit. pour it in the tank slosh it all arround let it dry and there you go. i used it in a couple of tanks i made for sandrails. if you have metal tanks it prevents rust. should work in anything though and it also seals up any pinholes. just my .02

A glass tank is made just like a boat, in a mold (or on a mold in this case), except on a tank, the nice shiney, hard surface is on the inside, not the outside. I had a 65 Howard flatty, sold it a few years ago, and it still had the original glass tanks in it with no problems. In fact when i was rigging at Howards in the early 90's we were still using glass tanks in the 21s.

But I have heard of others having modern fuel additives attacking the glass tanks.

It's the Ethanol they are mixing with gas nowdays, It dissolves the resin in the fiberglass, If there is a chance they use Ethanol in your area I would get rid of that glass tank and get metal tanks, It's cheaper than replacing a burned out hull.