Thread in general got me thinking... Is it really necessary to have a cush drive rear hub on a street ridden SM? Last summer I picked up a titled IT465 for the front brake for my YZ250 restoration project. The stock rear hub doesn't have cush drive, but they also ran knobbies on them back in the day. Not near the grip. Wouldn't care if it's hard on chain and sprockets. Hurting the trans would be bad. Good parts are a little scarce.
Thats a good question I am sure someone here will have an idea why. maybe check supermotojunkie.com and see if there is any info about it. My ktm 690 smc came with a crush.. I see some wheel companies offer you the option when buying them but it tend to be a lot more money.
Most, if not all, aftermarket SM wheels do not come with the cush drive hubs. My 450 doesn't have them, and haven't had any issues.
Bikes without a cush sometimes have transmission failures. Mfg's don't spent the money on a cush unless they feel it is needed. But then many guys get a way with it.. Ron
There's a cushion in the clutch basket on modern 4-stroke MX bikes, from what I was told that makes them work Ok in SM application. Old ones I have no idea about. FWIW say factory Husqvarna street SM bikes that are made on the Enduro platform (450, 510) have regular dirt bike rear hub. I have not heard of transmission failures on those.