Found this one late last week. Got it fairly cheap. Cylinder is cracked (how the hell do you do that?), piston skirt it broken off and in the bottom of the motor. That said, it's complete for the most part (side plastics are missing) and the crank doesnt' have any play.
Initially I was going to rebuild this one and resell it, but now the brother in law is making noises about wanting it.
I just put a new top end on my wife's 420AT, so I think what I'm gonna do is buy a new 500 cylinder and piston, put those on her 420, and put the top end from her 420 onto this one.
Anyhow, plastics need to be cleaned up, racks painted, will tear the engine down and clean everything out, new seals, new top end, new timing chain, then it hopefully will be good to go.