I have a liner, not exactly the same but no noise. Have you checked to see if the belt is riding on the edge of the pully? Might be rear wheel alignment? Belt tension, you should be able to flex the belt up about an inch with ten pounds of pressure. Extend the first and second fingers, push up with the top side of the index finger. The average person can push up about ten pounds. It is not critical.
Be sure you have not had damage by a stone getting cought in the belt. Look the pullys over for abnormal wear. Sorry that is the best I can do. I have seen a post on this, I will look for it.