Do a search for "hydrolock test." Somewhere you'll find a procedure here or on the other popular COG site where you can find out how to check and see if you have a bike there with a bent rod. Hydrolock occurs on these bikes when the petcock and carb needle(s) fail and a cylinder fills with gas. Then when you try to start it, the engine tries to fire and another cylinder's ignition stroke tries to compress the gas. Since a liquid (gas in this case) is not compressible like air, something has to give and it's the connecting rod. The compression will instantly be off of course, but with a bent rod, the height of the piston will now be changed (made shorter). Read the link and insist on it. You'll have to pull the tank and all four plugs. Read the link. Some bikes apparently run with a slightly bent rod for years, but you're better off knowing if you want to fool with it.
I think this is it:
http://www.zggtr.org/index.php?topic=272.msg2219#msg2219Good luck.