manual camchain tensioner fitment guide

[VNA]

Mike has been quiet for a while, maybe he's off on an Ivanising world tour!

£35 and half an hour of you time against the risk (all be it limited risk) of a big bang

Yeah, while I follow the logic, I'm not 100% convinced.  Also this is a part off e-bay.  Not sure who made it.  Are the materials and the head 100% correct?

I do see a company called APE making em - http://yamahazone.biz/tensioners.html

And they say;

APE manual cam chain tensioners are designed to replace the automatic and hydraulic tensioners on high performance engines. The automatic adjusters can back out when the throttle is closed suddenly at high rpm. This allows the cams to go momentarely out of time, and can result in bent valves and/or serious engine damage. Hydraulic tensioners have a tendency to put too much tension on the chain guide under high rpm/high oil pressure conditions, resulting in premature wear.  Both problems can be eliminated with the installation of the APE manual tensioner. No mater what the engine does, the cam chain tension will remain constant. An APE manual cam chain tensioner is a must for any kind of performance riding.
APE manual tensioners are CNC machined from billet alloy to exact tolerances for perfect fit.