On late model Kymco atv that have a speed restriction it is usually a spacer inside the CVT. You will need to remove the right side cover. Possibly the foot brake to get the cover off. Tap smartly with a rubber mallet or such. The front pulley set is your primary, remove the bolt, you will most likely need an impact. Use one cover bolt in the rear pulley set to spread the pulleys apart and take side pressure off the belt. You should be able to pull the outside pulley, roller weights and "fixed" plate out in one piece holding them together with your hand. There is a collar on the shaft that sets the minimum distance for the pulleys. Along with the collar should be a much shorter piece to make a "two piece" collar. Remove the shorter piece. Put everything back together how it came off but be sure to Loctite the front pulley bolt!!! Spin it by hand a turn or two to make sure the belt is not pinched or jammed. Remover the bolt you put in the rear set to spread the CVT apart. Spin another turn or two to check and make sure everything still looks ok! Button her up or if the rear end is supported off the ground you can start the machine and test the pulley set to be sure, then button up.
Also check the throttle, it has a limiting screw in the front. Make sure it is screwed out basically all the way so the throttle has full travel.
