Good question Phil ( I'm also Phil BTW
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Heres an answer. Sort of. Quite long.
Cam chain tensioners are one of those things that, through the years, have been troublesome on some bikes, and not on others. The first GPZ 900r's were notorious for having dodgy ones, and a few other models of bikes from various manufactures also had problems. Having said that, I have never had a problem with one on any of the bikes I've ever owned, and thats in 28 years of riding, and about half a million miles
Now, here comes the little problem that I can see with the Fazer one.
In the past when I have had occasion to remove cam chain tensioners from various bikes for whatever reason, they have all seemed to work on the same principle, which is a spring pushing a piston out from behind to tension the blade and the piston having splines on one side and a sprung toothed cam sort of thing which stops the piston from pushing back in. Simple really. If the spring fails in any way, the piston is locked in position and the first you would know about it would be a gradual increasing rattle from the cam chain as it wears and gets slacker but isnt being tensioned by the blade because the spring isnt gradually pushing the piston out to take up the slack.
With me so far? Phew.....
The Fazer one, or at least the two that I have now removed, dose'nt work like that. Rather than being a spring pushing the piston from behind, the spring is a bit like a minature slinky which is hooked over the end of the chain tensioner outer body, wraps around the piston and is hooked over the back end of the piston, under tension, and therefore PULLS the piston out, creating tension on the blade.If the spring fails at any point it will just close up and beome slack., doing sod all. Now, here comes the problem with this design. The piston isnt toothed, with a cam to lock it in place, so when the spring fails, it can just be pushed back in to the body of the tensioner, taking all pressure off the blade instantly, and then slap bang wallop slack cam chain flapping around, jumping teeth on the cam sprockets and then oh deary me disaster
![Cry :'(](https://foc-u.co.uk/Smileys/efocicon/cry.gif)
When this happened the other week, I wasnt even riding my bike, it was ticking over on the drive at about 1300rpm, and its still managed to lock up the engine and bend valves etc. Fuggin ell!
Now as far as regards servicing the little bugger, it shouldnt really need it. Its a pretty simple device really, fed by oil from the engine, and should be nicely lubed by that. Both times I've stripped out knackered ones, they've been full of oil and looking fine, apart from the snapped springs, which are really thin. I dont know why its happened twice, first one at 26k, second one at 32k, maybe I have an issue with oil flow, but it does'nt look that way. I'm flummoxed, and very very pissed off
So, it looks like I'm going to be looking for another cylinder head, and rebuiling it again, but this time I'll be buying a manual cam chain tensioner from somewhere ( seen one on ebay) and hopefully eliminating the problem
Dont let my bad experiences worry you, its just one of those things and was bound to happen to someone. That would be me
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Twice
Arse.
Sorry if that was a bit long winded, but felt the need to spout.
TTFN
Phil