Drive belt situation

Okay, this is a little weird (maybe). After installing my lowering shocks, I checked my belt tension (with the tension pusher-upper thingie). It was a little loose. So I tensioned it according to the service manual. I did notice that after tensioning and rotating the tire that the belt would slowly walk to the outer edge of the pulley, but not so much as to cause a bind. I wasn't concerned and rode like that for several months. Well today, I put the bike back on the lift to check it again. I spun the wheel in the normal forward rotation, with the belt quietly riding the outer shoulder. Got to thinking that maybe I had one adjuster a little tighter than the other, causing the pulley to be slightly cocked. I undid the axle nut, spun the wheel as before, and don't you know, the belt went to center and STAYED there, no matter which direction I spun the wheel. I'm thinkin' that maybe when I torqued the nut to factory spec, the friction of the nut against the adjuster sleeve pulled the axle just enough to cause the axle to be pulled out of alignment. Anyways, I left the nut at 65 lbs/ft for now, and will check it again later, for looseness


Has anyone else noticed this? Maybe there should be a washer behind that nut