Originally Posted by maurtis
I have decided that for this build I want to try my hand at making an in-frame gas tank. Probably fiberglass since I do not have the equipment to weld or braze on hand, but we shall see. So that means I will want a frame that suits one.
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.