Hi, i have a 2006 YZ450f , i purchased used, now i have noticed it seem to be a bit clattery noise at idle and lower revs, Eg putting through the scrub, the noise isnt there under under power, I have changed the oil and filter , no change noticed , is this normal , still has awsome power, next thing i was gunna take a look at is the timming chain tensioner? any help appreciated