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Message: [QUOTE="Rich Rohrich, post: 1017164, member: 16241"] They fail all the time Jay. On the CRFs we recommend people change the cam chain tensioner every season especially on 2022 & 2003 450 models. The 2004 and newer tensioner is a better design but I'd still toss it after a season of hard riding to play safe. There is something about the single cam setup that really seems to excite the cam chain. Early model Yamaha YZF450s tensioners are prone to failure, but the later versions seem much better. YZF250s seem to hold up pretty well but replacement every few years (along with the valve springs) is a good idea. Guys who don't change the cam chain every season on their YZF250s seem to have the most problems with tensioners. Probably because the cam chain starts the kink when it wears. I've never seen tensioner failure on the YZF400 & 426 engines but after a few years it's cheap insurance to change it anyway. RMZ450s have a manual tensioner stock that needs to be adjusted in the first few hours of running and checked about every 10 hours or so after that. Guys who don't rev them hard don't seem to have issues after the initial early hours adjustment. As for the RMZ/KXF 250 and it's much heralded valvetrain :rotfl: well lets just leave it at :bang: As for going to a manual tensioner on an engine that had an automatic tensioner to start with. I'm afraid you are blazing your own trail here my friend. Good luck with that. For the record, if you downshift ANY current four-stroke near redline and mechanically drive it past the rev limiter long enough and hard enough with the back wheel you are going to hurt the valve train, I don't care what kind of cam chain tensioner you are running. Nothing can be [b]foolproof[/b] because fools are far to ingenious. ;) The short history of what I've seen with cam chain tensioners. :cool: [/QUOTE]

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