Curiosity about variators

[RAM]

A friend has a 150cc Jonway scooter, and offered it to me. I been debating this all day, cause it does need to be tuned, and the 53mph is not bad for a older stock scooter. Still I am wondering about purchasing the bike, and would like a little more spunk. I know that on motorcycles changing the final gear at the wheel, going smaller, can increase performance and mileage, but I am unsure if it will have the same affect on scooters, or where to locate such a part of kit. Would this change help the scooters performance, and if so where can I locate such a variator or kit including the new belt size?