Yamaha TRX850 Enthusiasts Forum

I have a bit of a rattle which may be a slack cam chain (?)
Motor has done 35,000 miles and I have not touched the adjuster.
The manual says to remove the cam box cover to check the tension, timing marks etc after re-fitting the adjuster mechanism.
Is this really necessary or just the manual being a bit hyper-cautious ??
Any advice welcome.

Once you release the tension on the chain by removing the tensioner, it’s easy for a valve that has been depressed by cam to rebound and push the cam around and effectively change your cam timing because there is no tension on the chains to keep things where they should be.
Due to the nature of the 270 crank there is pretty well always an inlet or exhaust can or both with tension from the valve spring acting on it throughout the 360* rotation of the crank

Cheers Cobba

They do rattle a bit, I used to worry about my cam chain until I checked the valve clearances and opened them out a bit more.. Then it rattled even louder! Combined with the rumbly clutch it sounds like a bag of nails but doesn't seem to get any worse, I don't worry about it any more

And yes, the chain does always want to to skip around the cam sprockets when you let the tensioner off. I mark the chain and sprockets with a bit of Tipp-Ex first, then let the tensioner off and let it all do its thing.. Then just line the chain back up with the marks for reassembly. Turn the motor round by hand after though, carefully!

I think I cabletied my chain to the camgears last time I was reinstalling the cams, to save having to try to hold the 2 cams in place. But might be thinking of another bike.... Anyways, worth considering using 2 cableties if you do feel like replacing the tensioner.