I have a '00 yz 426--I recently had valves adjusted and runs great--note It has been ridden hard for 2 years. Last time out bike started making a "ratteling" sound-much more pronounced as revs increase--almost like a loose skid plate,pipe etc. I checked all things that could come loose and so far all is tight. The noise seems to be comming from right side of engine case.It has not lost any power even with this ratteling. It is loud enough to hear while racing(I race super-moto).Clutch actuation makes no difference. Is it time to have everything dis-assembled checked and rebuilt? If so what cost is to be expected? Sidebar--noise was less noticable a month ago and I removed cluthcover and clutch assembly--all appeared ok? Thanks for looking and any advice you may have is appreciated.