most of these 4 stroke 50 cc chinese scooters have a restrictor in the top of the carburettor,lift up the seat and undo the square insection panel there then undo the 2 screws on top of the carb and lift the cap off then you will see a nut screwed into the underneath of the cap undo the nut and replace the cap aking sure the rubber diaphragm is seated in the groove properly ,also they do have awasher in the variator on some maodels this can be taken out to improve top speeds and also there is a pink wire on the cdi of some of them that you can take off and it will make them rev more.i have done loads of them.
adam bike doctor(of milton keynes motorcycle centre)
June 2011