No, it should not spin the motor when off. I had the same issue when I first moved to a KT100 and clutch. If there is a a spacer, you may need to sand it down a bit – at least that is what was wrong in my case. If the starter nut is coming off, check the bearing in the 3rd mount. If it is not spinning freely then it can cause the starter nut to back out. This ruined my race weekend a couple months back.