I believe the JS are just to align the chain. With the cvt you don't need reduction. I run 212cc with 2" pulley to a sheave. Others who run chains are all different depending on what they want top end or fast take off I've seen 41t,48t and even a 32t rear sprocket on a chain drive directly from the cvt. I'm sure some so run JS with some kind reduction. Just spitting out what I've seen.