I've heard that one of the wax manufacturers makes an "etching" wheel cleaner that works really, really well on airhead cases. Mother's? Meguiars'? I wish I could remember.
It's made by Eagle One, It's "etching wheel cleaner" Motor before Jug before Jug, head, motor, and tranny after 1-2 treatments. It takes a bit to get all the deep down stuff out. I also found it helped a bit to heat the parts in hot water, apply the cleaner, scrub it good, rinse and repeat. Mike P.S. Look in my "Winter Project" thread for more pics and results.
