hi guys, i have a little yammy aerox 50 scooter 05 reg & have just had fitted a sports exhaust to get a bit of extra speed, i also changed the variator rollers & clutch springs but from a standing start the pull away is very poor up to about 12 mph then it flys along perfectly. i havent touched the carb at all so was wondering if i need to adjust the mixture screw, or up jet, or raise the needle ? please please help !!!!!! thanks