I've tried POR 15 and Hersh motorcycle tank sealer kits for my early fastback w/a fiberglass tank. Followed all directions let the tanks cure for over a week without fuel, but the available gas w/15% ethanol after a while breaks down the sealer and it starts to come off the sides and fouls the pet cocks and carb sides. Any ideas

Caswell has a new fiberglas tank sealer. I've heard it works well. Here's the link http://www.caswellplating.com/aids/epoxygas.htm

Dave

If you consider the Caswell Sealer gas tank sealer on a fiberglass tanks, take a handful of drywall screws and shake them around inside the tank for a few minutes. This roughs up the surface of the tank, providing best adhesion for the sealer. Follow the mixing and application directions that are printed on the product.