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hey, i bought a zx50 off a friend a while ago and never really had any troubles, untill i tried fitting it with a new clutch bell spring, dr pulley rollers and unrestricted cdi, at first it would max out at 15km.. then i bought a new belt (thinking that was the issue) fitted that with the stock spring and the dr pulley rollers and same thing but now it spits out excessive amounts of smoke.. now ive removed the unrestricted cdi and put the stock on in, less smoke but still maxing out at 20km.. please can you help me!!