I have an 02 with a lot of miles... The primary has grooves from the belt about an inch and a half up from the bottom on both shieve faces. They are not very deep, but they are there. Is this going to effect performance at all and can they be sanded out? I have a rebuild kit on the way, but I'm starting to think it may just be time for a newer primary.
The 8DN belt is one of the strongest belts out but unfortunatly one of the hardest also, those marks are from intitial engaugment. I would not try to sand them out, I have ridden MANY miles with slight marks just as you describe them. I would just keep an eye on them and make sure cracks dont develop. I am sure other opinions will tell you differant, just my 2 cents.