Ok, went to start the 450 awhile back. Kicked over the bike and the kick starter stopped, wouldn't go down any. Long story short, empellor on water pump was torn up with a piece of metal in it. Don't know where the metal came from. Took clutch off and turned the crank, it turned and then stopped and wouldn't turn anymore. Turned crank backwards and it stopped again when the piston reached the same point. Thought to myself something was on top of piston keeping it from moving any further. Took off the head and turned the crank, this time the piston turned freely all the way through the cycle. I looked at the piston and the top was scratched. Anyone with any ideas? Valves appear to be fine. The torn up empellor has got me confused, where did the metal come from? Could the empellor problem be related to the crank problem?