As for centering the belt...
I find that my belt refuses to stay in the very center. My current adjustment is the best that it's been since I've owned the AK. My belt has been very consistently 2-3 mm from the outer rim of the rear sprocket since the last time I replaced the rear tire. Up until that time, for the first 2.5 years The belt was often drifting from outside to inside on the sprocket. The important thing to know is that the belt must be set to be a minimum of 1 mm from either rim of the rear sprocket. I haven't looked for a while but I was sure the Owner manual states that. I do have the service manual downloaded and it gives a detailed explanation of how to adjust and where the belt should sit.
As long as the belt doesn't touch the rim on either side. 1 mm is about the thickness of a standard (flat) screw driver blade, usually. Here's a series of photos for when I adjusted the belt adjusters.
https://photos.app.goo.gl/Kf1x6Dw1tC51mwHg6Aside from the video in the post above there are many videos for adjusting the belt on many motorcycles with a belt final drive. Almost all are the same procedure.
The manuals for the AK show using a sonic tension meter to adjust the proper belt tension. I'm not spending the high cost just for one device that I will only use for one thing on the rare occasion that I would need to use it. I decided to follow the method used by Harley Davidson owners for their belt final drive bikes. I bought a belt tension tool from Amazon. I found the center point between the front and rear sprockets and use the tool on that point along the belt. When I first bought the AK I checked the tension to get a starting point for what tension is needed. I found that pushing up on the bottom run of the belt along the mid-point with the tool the deflection needs to be between 3/8 and 7/16 inch at 10 lbs force. Here are a few pics and a short video how I check this.
https://photos.app.goo.gl/25dydWo8FZ2szXS17Here is a link to the tool I bought.
https://a.co/d/3XKu9S3If tension is too tight, meaning more force needed for 3/8 inch deflection, then the belt needs to be loosened just a very little bit. If tension is not enough, meaning more than 7/16 inch deflection at 10 lbs force, then the belt needs to be tighter. This is the part that takes patience and time... usually. Have the axle nut making full contact but not tight. Not loose either but just so the axle plates can slide. Check alignment and tension again after tightening the axel nut to torque spec.
I cut a slot in the inner bottom belt cover that my tension gauge fits into to allow me to hold the gauge straight up. Another owner who followed my lead on this and posted a YouTube video on it actually removed the belt holder on the gauge and put a hole in that inner cover rather than a slot. I felt the belt holder was needed to avoid damage to the belt.
