There are several reasons a sprocket can be wobbly like that. I'd certainly suspect the machine shop, but I have had to mess with plenty of Cat sprockets because of bearing alignment, and microscopic wobble on the mounts. And these were factory setups that had been on the bike for over 40 years.
There are several posts here on sprocket alignment that I used a few years ago to guide me. Throwing it out there- might be the machine shop mistake too.
There are several posts here on sprocket alignment that I used a few years ago to guide me. Throwing it out there- might be the machine shop mistake too.
I recently bought a blank sprocket from OldMiniBikes. Had it drilled and the chain ran too loose to too tight. Figured the holes were off. Made the holes bigger and then even oblong-ed them for maneuverability, but nothing made any difference! I changed the sprocket bearing too, but still no change. Finally I took the sprocket off the wheel (bearing intact) and put it on the axle and mounted the chain. Guess what? The chain STILL ran too loose to too tight!! To me this means the holes (mounting) were not the problem but the pre-drilled center hole is off. Am I in the ballpark on this?? Thanks for any help.
I ordered another blank sprocket from OldMiniBikes and this time the bearing hole is properly centered and my too loose to too tight chain problem is cured!!! I now realize the drilled mounting holes had nothing to do with the problem. I even drilled the new one myself and it works perfect. It was all due to the bearing hole being off centered. Happy day!!!