piaggio zip sp 50 Liquid Cooled Power loss?? help plzz?

hi all, i've tried my hardest to sort it out but it wont go away, when my bike is cold - coldish it will pull away quite fast, but when its at normal operating temperature it wont,it'll pull slow but after 5-8 feet it drives fine until i stop and have to pull away again, its almost as if your trying to pull away in 3rd gear in a car. ive changed :

Piston, rings and small end bearing
changed the variator
fitted race clutch
up jetted carb (professionally done)
Gianelli exhaust
NEW automatic choke.

any advice would be appreciated thanks