Ok so I have a 04 YZ450f keep up on maintance, not too many hours on it, not sure the real count, but was trailriding with my friends, we were pretty much wide open, let off for a corner and she locked up on me..so I've torn it down and indeed the big rod bearing appears to be locked up, I can move it just not very good, def my problem area, so this is where I'm baffled, there was oil in bottom end, head, cam, valves are all fine with oil, and cylinder is good too. Wristpin is free as can be the only thing that appears to be damaged is the big rod end bearing. The rod doesn't seem to be discolored or anything like there was a excessive amount of heat, also it appears everything else (counter balancer ect) all turns freely like it should. So I guess my question is what can cause this failure. Guess I've never had one lock up that had oil in it. I just don't want to put it back together only to have it do it again, but I'm not real sure where to start trying to find out my problem. Any thoughts, or suggestions would be appreciated. Thanks.