These new 225cc kits from S3 are excellent. Developed by Julian Wigg, Kev Hipwell and Michel from S3 in Spain.. They are a modified 250cc cylinder to be fitted to any PRO125 or 200 bottom half engine. For those who want to convert their 125 if your son/daughter is now out of the Youths then this could be a very good option if you can not afford to swap bikes. Also for thos eof you that want more power from your PRO200 which are actually only 167cc !.....In the kit you get the 225 cylinder, piston, head, base gasket and head o-rings. We also advise fitting a flywheel weight which are also available for an extra £32.00