theres a screw in the lid of the carb which restricts throttle height, some are restricted by the size of the jet and a block in the airbox, and some are restricted in the variator you also need to set the needle washer to the middle groove.
actually the keeyway is taiwanese, built by the same company as sym inder liscence and inspection from honda. therefore not "chinky shit!!" i'm not familiar with this model but i would immagine its a variator restrictor and/or an exhaust washer or restriction pipe.