the dr. pulley Wt.s and sizes you are looking for are 20/12 and the wt. is your choise, 12 to 15 grams the popular one is 14 gram it gives better take off and same or a little better top end, if you want just better top end go for 15 gram,. that is what I use , my scooter seems to pull well all the way to 80 mph. no flat spots, I have 45,000km. so far and feels like it is still getting better, as I put the milage on,. well best of luck and safe riding,.