Aerox wont rev out

I have a 70cc polini corsa aerox with a pm tuning crank, but i had to change the clutch as it was knackered so i went to start it to go out after building it back up and it would not rev at all but would idle fine, so i completely stripped the engine to see what it could be, changed the electics, cleaned everything, checked the carb like 3 times and it would still do it, ive been reading it could be the crank seals if so i will be over the moon and just change them

 

might sounds silly but has the throttle cable come off the throttle body

 

Sadly no it hasnt:/

 

It does rev, but it misses, smokes alot and backfires

 

have u checked to see if its running rich

 

I premix it, it was running fine then just done this

 

Check for an air leak on the inlet manifold? Otherwise, it's probably crank seals.

 

Im positive its probably crank seals now, i have my mind set and i will replace them

 

I have same kit and i run it on the standard crank and i haven't had any problems with it, Thinking about getting a new crank soon

 

My crank has made such a big difference well worth getting one

 

You notice any performance?

 

Yeah it will lift without trying

 

Just what i like to hear i think my jet is too high atm i'm using a 92 on a polini corsa 70 + stage 6 pro rep exhaust