Those CH80's could use a few tweaks. My first scooter was one of those. Make sure you have
room for the belt to go out further on the variator then you might try doing this;
Just make a depression so the roller can move out 1mm, then make sure the two pulleys can
get closer (you might need to take 1mm off the hub of the fixed pulley).
Lighten the rollers a little and she should be singing...