A friend who is a long time bike restorer told me he has been using a Poly Sulfide two part tank sealer on metal tanks for many many years with no failures so far. He buys the stuff in bulk from some industrial supply place & as directed by a chemist he thins it with MEK. It cures at 77 degrees for 10-14 days and then is a coal black thin elastomeric coating that in all our tests has not been afected by modern gas. I just noticed that it is sold in the "Aircraft Spruce" catolog and called "Pro-Seal" PE-1776M. We sprayed a plastic dish with teflon form release, poured some in let it cure & it penetrated the form release & stuck to the plastic dish so good we could allmost not get it out!! This leads me to think it will seal & stick to fiberglass very well. It won't crack because it stays flexable & SO FAR, not been harmed by gas. The bikes my friend has used it on are in many places around the world. Just wondering if anyone has heard of it???

The aerospace division of the company (PPG) I work for manufactures PR-1776 as well as several other polysulfide tank sealants. When I checked into them a couple years ago, the technical guys in that division told me that these are either extruded or spread with a spatula as they are quite thick. It is designed to be applied to components of wing tanks, etc. and not as a "sloshing" sealer. They also told me that they have no history of its use on fiberglass, especially if it has already been used for gasoline. If MEK will thin the stuff sufficiently, then it could work. I could not even finagle a sample from the guys, and since Aircraft Spruce sells it for $256 for 24 oz., I think I know why!