I was able to take my new 06 450 out this weekend to break it in (by the way, I love it). While taking a few mellow break-in laps, one of the chain adjusters loosened-up and the axle slipped. This caused the wheel to become misaligned and the chain to go really slack. I took the bike home and removed the rear wheel to inspect. Everything looked fine. I went back out today and noticed that when I decelerate, I "feel" a strange vibration. If I pull in the clutch it goes away. My gut feel is that it's coming from the engine. If so, I suspect that the counter-shaft bearing may be bad. Any ideas? Since it's brand new, I'm going to take it to the dealer. Otherwise, the bike is GREAT! Feels very much like a 250F with more power. Well worth the wait.