My son's '07 YZ450 seized 3/4 of the way through a mostly high speed MX style enduro 75 mile today. The bike has never used any oil before but I checked the oil before the race and it seemed a 1/4" low, so I started it and let it idle and shut it off for a couple minutes and checked it and the oil was a little high. The bike seized during a long straight where he was riding 5th gear pinned. When it seized, the rear wheel did not lock up, and he was able to coast to a stop. After we got the bike off the course, the dipstick was dry. There were no signs of any oil leaking or blowing out. When we drained the oil we only got a few oz. of black and what seemed like very thin oil. Can you guys think of any explanation where the oil could have gone? It might not do much good but it would be good to know if a failure could cause the oil to go somewhere or if lack of oil caused the failure. The exhaust was pretty much dry and the antifreeze was an oz. or 2 low didn't seem to have oil in it. We put a new clutch in a couple of weeks ago and the new clutch seemed to be working perfect. It had about 75 to 100 miles on it. At this point, it is impossible to push the kickstarter down. We also noticed that when keeping the bike in gear, and pulling in the clutch, the bike moves with zero resistance. In the past, it has always been difficult to push the bike in gear with the clutch in compared to pushing it in neutral--now they feel the same. Could this have something to do with the failure? But even it did, I still don't know where the oil could have gone. With a seizure like this, what are the odds that this damage could be limited to the top end only? Thanks in advance for your ideas.