problem with speedfight 100... what a suprise :)

im sure i spend more time fixing it than riding it -.- my name is Richard and im fed up i have a speedfight 100 that is ruining my scooter life what i have done so far taken the carb off and soaked in carb cleaner new plug new air foam it has a new exhaust as the old one snapped -.- iv taken the restrictor out of it now my problem is before the exhaust snapped it used to go 60 well now it revs good till 30 but after that it takes ages to get to 40 and wont go any more the exhaust put on is the same as the one that broke also i reset the fuel screw to 1 1/2 turns i do keep tweeking it to see if thats the problem any ideas would be great as this bike is driving me crazy thanks rich