Like Barker says, "Airplane Stripper" get it at any auto parts store. The stuff will make paint start to fall off, even modern urethanes and powder coat finishes. Then use something like a wire brush and hose to knock it off. Rinse and repeat.
I just used it on a factory powder coated crankset, 3 minutes and I could take the paint off by tapping the crank. You will just wanna slap those people who recommended anything else.
PBR, Jasco may be nasty to humans and other organics, but it isn't nearly as good as this stuff for stripping a bike frame. Really. Not. Even. Close. The next time you need to get paint off of metal, try it. Honest. You'll thank us.
Last edited by Ronsonic; 07-10-09 at 10:43 PM.