If it’s abraded on the non-ribbed side, I’d suspect a failing smooth idler (can’t recall if there is one or two). Rotate and listen for clicking, grinding, or resistance. Wiggle to check for axial play. If you spin it hard, the idler should continue on its on own for 7-8 seconds.
The tensioner should move a little by hand, but should require the leverage of a wrench to really compress it. Attach a 14mm socket to the center bolt and push up. Remember it’s a left hand thread, so set the wrench as if you were LOOSENING a regular bolt.
If you need a new tensioner or pulley (and can wait), today is the last day of the SE Dealers 20% off sale. There’s a long thread about these sales, I buy from Serra but there are few others.
