WALL all of the nexstars are supposed to have been broken in from the factory, the trouble your having is typical of mostly all of the nexstars. you have to adjust the lower end mixture screw, i would start buy turning it in buy an 1/8 this is the screw at the bottom of the carb, you will also have to change your mixture screw as well,when it is adjusted correctly you should be able to snap your throttle and the motor should respond emediatly.