Hi. Ive got an o6 cooper S checkmate. It has the JCW exhaust but that was all i thought it had as there is no plaqe on the engine and the airbox is standard. Ive just bought a 15% reduction pulley plus the tool to remove the origional pulley and the garage just called to say the tool is too big to fit the pulley! The pulley that is on there doesent look like an aftermarket one, its a black one piece item. Is it possible i have the JCW supercharger and pulley? If so is that a 15% pulley already? If i measure it will that tell me anything?

A black one-peice pulley could be a JCW 'charger, in which case the pulley is 11.3% smaller ... based on a stock pulley diameter of 65.5mm and a JCW pulley diameter of 58.1mm.

The previous poster is accurate. I would suggest this kit
WMW Pulley Package - Way Motor Works (http://www.waymotorworks.com/wmw-pulley-package.html)

Thanks for the info. Looks like i have the JCW supercharger then. Next question then. If the JCW pulley is an 11% pulley i guess im going to see some improvement by fitting the 15% pulley i bought. Only problem is how do you remove the JCW pulley as the tool is for standard size pulleys and does not fit?

Also thanks for the link to that kit but i wont be needing it as i bought new plugs, belt and also some bit of kit that goes on the intake i think that has a stronger spring in to make sure it shuts and you dont get a boost leak.

Oh also, will the belt i bought to fit the 15% pulley fit on ok if i left the JCW pulley on for now?