From what I have understood, (and I could be totally wrong) cush drives and rubber dampers in CS sprockets were put on bikes to keep the transmissions and clutch baskets from being torn up from shock fed though the chain drive when the tire has plenty of grip. On a dirt bike, the tire is always in some state of slip but on a road bike, all the shock waves from the road and motor get transmitted through the parts with slop in them such as transmission teeth and the ears on clutch plates which are much softer than gears. Once you have those dents beat into the basket, the tabs want to ride there instead of moving on an even plane causing either drag from not being able to move apart or slipping under power from not being able to slide back together until the power is let off. (I think I typed that right :huh) I did have to file one basket to get it smooth so my clutch would work properly, I believe it was my KTM 495 It also dampens chain snatch and from what I have read, helps eliminate spline wear on the coutershaft sprockets. Some bikes had spring dampers in the clutch baskets also. I switched to a solid JT on my 950 and it feels like there is much more unwanted vibes coming through so I will be going back to a dampened unit when I replace the chain. One of the articles I read years ago talked about testing their motocross engines (I believe it was KTM) in street bikes because the wear and tear on them would be more dramatic per hour than if they tested them off-road. One of those items they were testing for was drive train durability due to riding on pavement. There is a lot of force going through those parts. My 86 Can-Am 560 Sonic used to eat swing arm [needle] bearings on the drive side. They didn't rust or seize, the outer race would literally be pounded thin like smashing a penny in one of those souvenir machines or under the wheel of a train and expand almost a 1/4 wider than new. I found a way to get 2 narrower bearings from a Husky which added up to a wider width a to fit in the space allotted with a little modification. I never had to replace the non drive side. The rear wheel also had 2 bearings on the drive side vs one on the non-drive side. My TA's chain is getting due for replacement so I'll find out soon what those splines look like. One thing I do know is none of my Euro bikes use the keyed keeper to hold on a floating sprocket, they are all fastened solid via retaining nuts. All my XRs and XLs prety much have had the same spline/sprocket set up .