So I got a 2008 model fairly recently, and this being my first motorcycle, I'm still trying to get the feels for what is normal and what isn't. It has already seen ~90k km, and I'm the 5th owner, with the 4th only owning it for a few month so maintenance records are close to non-existent.
(Almost) everything felt fine enough for a newbie like me until recently, after riding it for ~1k km, it developed a new rattling noise in the left side engine cover. I knew the doohikey had not been replaced (said the previous guy) so I took the occasion to do it, bought Eagle Mike's and when to town.
Upon opening the left cover, it clearly became apparent one of the previous owners had a very straightforward approach to mechanics, one that did not very much care about anything but the short term end result.
The screws for the two layers of the cover and the sproket guard (different length) where happily mixed together and 3 had been replaced by whatever the guy had lying around - ones with heads too big that were a real pain to unscrew.
Inside, I found that the spring was missing, the original doo adjusted to maximum tension (completely rotated clockwise), and tension adjuster bolt (the one accessible from the outside) had been cut. The two functions of the adjuster bolt where now shared by a new, short screw to block the adjuster, and the remainder of the original bolt (the part with the o-ring) to plug the hole in the cover. The OEM doo itself looked perfectly fine though.
Also, lots of scratch marks on the inside of the case, and the inside face of the chain, I assume from the spring breaking loose and getting in the mechanism. And places where the chain started to saw the case (under the tension adjuster gear mostly), the usual >_>.
Pics here : the bolt that has been cut, the doo before intervention, damage to the inside side of the chain :
The thing I'm not sure about is the length of the balancer chain. Now that I have a clean doo installed with torsion spring, the tension adjuster gear shaft seems to be rotated so much that it pushed the chain very very close to the case. And when I try to pull the chain perpendicularly (before tensioning) it has quite a bit of lateral play.
So here's the question: how would I estimate if the chain needs to be replaced? as far as I can tell its damage seems, while visible, still marginal. Yet the way the previous guy did things (put as much tension as he could and leave it there with no means to adjust it again) seems like a recipe for premature wear to me.