Originally Posted by trug
Beware Ethanol eats fiberglass, not fast, but it does eat it so error on the side of thick 'glass, and don't store the bike with corn gas in the tank (if it is going to sit for a week or more drain the tank.) If you do get a leak, regular JB weld wont cut it, use the stuff that comes in a tube that you cut off and kneed together J-B Weld Company - WATER WELD Product Information
, give the tank a few days in the sun to get the gas that has worked its way into the glass laminations a chance to get out. Put the putty on, it can be sanded, and with some bondo you can hide the repair.
Also most tank lining compounds don't stick to the polyester resin in fiberglass very well and end up clogging the fuel line.
Just some practical advice from someone who rides a 35 year old motorcycle with a (very difficult and expensive to replace and occasionally leaky) fiberglass gas tank.
now why would you want to coat/fix the outside when the damage is coming from the INSIDE of the tank. Its like using a bandaid on a gunshot wound caused by a shotgun. CASWELL epoxy tank sealer is not affected by ethonol.
You may own a old bike but you don't work on bikes for other people where I do and as far back as the 1920s.
Live life as its your last day... it just may be
Learn to do it right or how to fix it later, quicker to do it right the first time.