clone gx200 help

I got my ct200u about 3 months ago, everything was running good and a couple days ago it just stopped accelerating, i took the governor out about a month ago and never revved it to crazy limits. I took off the side cover, checked valves. It has compression (around 90psi), spark is good, carb is...

My friend has 6 baja carbons with 6.5 motor, all we did to them was unscrew the throttle stop screw but for some reason two of them are a little slower, 2 are in the middle and other two are way faster than the others! Any ideas on how to help the slower four out??? Their all stock...