It's "scary loose" on the S3, and I don't have a problem with that, it's just that it's kissing the top of the swingarm at times when ridden. It's left a black mark on the swingarm. Too loose? Seems like the contact would eventually wear down belt lugs, no?
I brought the swingarm up so the rear axle, swingarm pivot and trans output shaft were in-line and then adjusted belt tension to be snug, but still able to be flexed upward about 1/4".
I had mine like that for many thousands of miles without issues and then one night, it ate all of my teeth off!
Smarter people than myself told me that if it is too loose, the teeth won't be supported or something.
Obviously, if it's too tight, It will ruin bearings or snap. I tightened my replacement so that I can touch the top of the swingarm but not so loose that I can touch both top and bottom at the same time like I had before.
"It's better to be too loose than too tight." Talking about just the belt right?
I run mine just about as loose, but I check it using my buddy sitting on the bike. Just loose enough to where the belt almost touches the swingarm on the bottom. Without any weight on the bike it pretty much looks like in PK's video
yeah it's not as sloppy with my 130 lbs on the bike. I had it adjusted tighter before, but realized that with weight on the bike it didn't have much slack at all.
The belt also gets tighter as the engine gets to the operating temperature. I am sure someone here can explain why that happens but it does. I have mine set just a tad tighter than PK and after an hour ride, with me (140 lbs) sitting on it, it feels much tighter.
Running mine at about the same looseness as PK's I don't have a problem with it rubbing the top of the swingarm. I haven't checked the underside of the swingarm to see if it rubs there. You should tighten it just a little to stop the rubbing. The rubbing of the belt can't be good for it. Just my 2cents.
I just changed my tires and adjusted my belt to about as loose as PK as well. Shifts a hell of a lot easier and not missing second gear shifts under hard throttle anymore either.