so recently my 2003 YZ 450 bent the 3 intake valves. However, the cam chain was replaced in January 08, along with the piston and rings. upon inspection, the tensioner is working fine, not as strong as the new one i got for it but other than that it works proper. I work at A yamaha Dealer, and some people have said the cam seized in the journals, thus causing the chain to jump and the piston to hit them, and my machinist ( Wally Routledge) says the piston hit the valves, causing the cap to bend a tiny bit, seizing the cam after the initial hit ( hes the one who repaired it) I did replace the clutch friction plates, steel plates, and springs about a month ago ( about 20 hours use before valve bending) , anyhow i found out earlier this week that i accidentrly installed a WR426 clutch.... my hinson clutch basket shows a bit of wear, but not as much as i see in the bottom of the cases and in the oil filter so the question ihave , is why did the timing mess up, causing the bent valves, and why is theree so much sediment? if you need any more info please ask, but thanks for any help!