Been talking to some sportster owners and I'm getting a lot of different info on the spacing between the frame rails and the rear pulley. Why does this change from year to year?

I have a 2000 and I was wondering what mine is. I've got a bit of a basket case right now, but I threw the axle and everything on it together in a hardtail I have laying around, and my gap is slightly less than 1/16". It seemed a little closer, but I have all the spacers and in the correct t orientation.

If it matters to anyone I've found that an 06 is 3/8" and an 02 is .213"