The manual has a diagram that shows to measure the slack at the bottom of the chain. I tried to find the tightest spot and found that all portions of my chain had equal slack. Maybe that's typical of newer chains and as they age they develop tight spots?
I initially used the hash marks to align the rear tire after tightening my chain and a quick test ride told me this wasn't good enough. I used this method to re-align and it worked great:
I've got a similar question regarding chain tensioning. AFAIK I have to measure the chain tension at the spot that's in the middle of the chain horizontally. I measure the slack between the lowest and the highest points of the chain at that particular middle spot. The lowest point is easy to find but the highest one - it seems to be the plastic chain guide right above the chain. Is it normal for the chain to touch it or my chain is too loose?
I measured ~50mm from the lowest point of the chain to the plastic guide which is OK according to owner's manual. On the other hand I don't know how much more the chain would go upward if the chain guide wasn't there.
I definitely measure it below the swing arm. Maybe "plastic chain guide" is not the correct name for the thin plastic thing that runs along the swingarm and keeps the chain from scratching the swingarm (I attached an image just in case). Anyway that's what I meant - my chain touches this plastic thing and that's what I'm worried about.
Couple items...
Are you measuring deflection at a point halfway between the center of the two sprockets? When I first attempted to measure my chain slack, I was surprised how far off my estimation of the halfway point was located. I actually measured the distance between the two sprockets and located the halfway point.
Measuring with bike on center stand? With my chain slightly outside spec, maybe 57mm, I couldn't make it hit the guide on the bottom of the swing arm.