i had exactly the same problem your jet is too small i put a 80 on mine with a polini performance double sponge air filter there is also a brass filter in the carb you could remove that depending if it is running rich or lean! Piaggio NRG FTW
Cheers bro! My mate told me that he has a 80 jet. His runs fine. Think i best get one then an the brass plates gone.. Cheer for info!