Those bikes have slipper clutches in them stock from the factory. All you need are different thickness friction plates and spring (to get the slipper fuction working). If you do a search on this site and a couple others (
http://www.redmonkey.com,
http://webzxr.co.uk/) they will tell you how and what to do. Most people who use this bike on the track and have done this adjustment say they love it (helps going into the corners).
