
The tensioner should be on the front of the engine, to one side I would assume. A couple of bolts with a round thing in the middle. Gee, that description narrows it down, eh? Maybe someone else with the same/similar bike can take a photo for you so you know what your are looking for.
Wouldn't expect a lot of slack at 25,000km though...why I think it may be something else...

man I need a coffee...