i picked to go one down in the front and 2 up in the back.....which made my bike extremely fast off the line but that was it. For south florida professional riders this is garbage!!!! it revs out way to fast and you will get left on 95. it comes up in 1st, 2nd and 3rd if your nice. i went back to the standard 16 in the front and 1 up in the back. It like it a lot better it revs more acceptablely, i can crusie in 1st at 6500-7000 rpms in stead of the 8k that the 15 front did. If you like your top end and can get there and stay up there i wouldn't go any more than one up in the back LEAVE THE FRONT ALONE. until you have a enough power to go one up. if you need a little help on the wheelies in 2nd i would get one up in the back it will also stand right up in first. [:-]

 

Stock here is 40 T Rear, I believe the US got 41 T rear as stock. Don`t know why? ? but your rear sprocket has the number of teeth stamped on, easiest way to find out.