I've used Red Kote on two tanks with pinhole or seam leaks. Worked like a charm. Bought a quart from O'Reilly's and barely used any of it. Just followed the instructions. I think the qt can was about $28.

Ok thanks guys. I had already picked up a container of sealant from Eastwood just for small fuel tanks. I hope it's as tough as the red stuff. As far as ruining the tank, if I can't fix the leaks then it's useless anyway. Sounds like prep is the big key, starting off with the cleanest, driest surface possible.

I use acetone to clean tanks when I coat them, just pour about a cup in and swish it around and then drain in. The acetone will evaporate pretty quick leaving a clean and dry tank.