Re: Keeping chain out of spokes???
Thanks 2door. I did check the sprocket before mounting and it was nice and flat so that's a blessing and the hole for the hub was also stamped smack in the middle of the sprocket. (I wonder if anyone has had a stock sprocket with the hole stamped off center on these things?) Anyways, I did check the concentricity to the hub which is perfect as well. In fact when I went to mount the sprocket out of the box it was slightly tight on the hub so 2 quick careful passes on the inside with a file made it fit the hub perfectly.
So it's just the side-to-side runout that's the issue and I think the discs are the culprits. They were of uniform thickness but not uniform composition. Looking at the side cross-sections one of the discs looks like plain rubber whereas the other has some fibers embedded in it. So I think the discs would compress differently. And to get the sprocket to the current runout not all of the bolts are tightened to the same torque. Some I had to tighten more and some less no doubt because of how differently the discs compress.
McGyver could fix that with bubble gum.