This is my first go round with a motorized bicycle and I do know I have a lot to learn. After buying an Ebay kit I bought 2 more counter sprockets and another rear sprocket before I hit on something decent enough so that the chain would ride the teeth half way acceptable. After getting mine aligned I just ran it until the chain and teeth wore in enough to quiet down. I saved the worst counter sprocket. It's amazing how distorted the teeth are.
After getting it aligned the chain would still go tight, loose, tight, loose because the chain wouldn't ride down in the teeth the same amount as the gear turned and the rear sprocket was out of round.
I've read threads about filing to shape teeth points and I realize you get what you pay for but having to file down in the sprocket teeth for pitch seems just not worth the effort for me. I was ready to throw the towel in and call this project. This big sprockets are not near concentric and slightly warped.
I would have tried the CDH Power CNC rear sprocket but couldn't find a CNC counter sprocket. I gave up rather quick on my search for these items. I didn't want to match a good rear sprocket...if the CNC sprocket is in fact good... with a trash counter sprocket. As I wrote above, I got it close with a couple of the sprockets and ran it until the chain and teeth wore in. It's far from being correct but it's a lot quieter now after a few hundred miles.
To answer the starter question...I think these sprockets are cut out and stamped out by many different manufacturers with no sort of quality control to match the gears to a 415 chain... all the Chinese 415 chains are probably different too.
My limited experience is the sprockets I bought from all different vendors were all distorted in different ways. I'm running the 44T and really would like to try a 40T but I'm just not ready to go through this rigmarole again.
