Re: i think my "80cc" has issues. top speed only 28mph with shifter kit...
stock main jet is around 0.070 mm My engines run the best on 0.065mm main jets.
check your needle for taper I think it should start out by the clip grooves at 0.070 and taper down to 0.065 those numbers might not be right but if you can mic your needle it needs to have a taper. Pablo had one that didn't have the proper taper and it would not rev up at all I worked on it and got it to working good on my bike then I shipped it back to him I guess he either shelved it or put it on his bike.
If you want I can have you send me your carb and I'll test it on my bike and see if i can do some mods to get it to perform all you need to do is pay for the shipping. I have 70cc and the cough, cough, 80cc engines to test it on.