Peugeot speedfight 100 cc

For sale is my speedfight 100cc 4 months mot full logbook runs but doesn't pull properly will pull off slow an only do 25 mph not sure what's up with it I've changed the rollers, clutch ,belt an clutch bell its blowing abit from the exhaust so could be that it need back brake line putting back on an bleeding too just haven't got the time as I need a bike for work an I dont no much about scooters