I was reading this thread and I related to your hesitation issue/ occasional stalling and I have a little bit of scooter knowledge that helped me build my hypothesis and hopefully solution. The bike I purchased recently had been layed down reasonably hard and I have done some work to it. I got it running only after I put a new cylinder and sleeve in it because there was very little compression. Come to find out once its running it is having the same behavior as yours. Now I took the CVT case apart because it was the only thing I hadn't touched yet on this bike and lo and behold, the belt is showing signs of age and there is belt dust everywhere in that case. I have a longer overdrive belt on order now which I expect will solve the slow in the transmission on the low end and stretch out the top end. My scooter has 12k miles on it and I don't see any sign of belt maintenance before me, the cover gasket was still all there and in one piece.
Reasons for the driving behavior being the belt are as follows. The variator pulley is making zero contact with the belt due to it being too narrow, this doesn't move your clutch pulley smoothly but rather dumps a large load on the motor when the variator finally does open up a bit. Next, you have a lot of slack from a skinny belt that isn't accounted for which will ruin your top end as it can't ride up your variator effectively. Stalling or lugging while slowing down is also from the belt slack I believe because it is possible to overrun the transmission especially while going downhill and the motor isn't rotating as fast as the belt might be with the slack in the system and when it does grab eventually it is engine braking the whole scoot randomly. Hope this insight points you in a useful direction! Check the CVT if not for maintenance, then for upgrades! My goal is 80mph and 80mpg out of this thing!
