well to make a long story short, I recently lost most of my oil through a missing valve cover bolt and discovered that the cam journals were basically toast. I replaced the head on my 06 rmz 450 with a 07 head from ebay. Bike ran for 5 hours after rebuild until seizing after landing from jump. (motor abruptly stopped and kick starter would not move,) I figured the crank bearings went from the running it on low oil before rebuild. took of cylinder and head and noticed no visible damage and my crank moves! I'm stumped, any ideas?