Hello can someone help me? I am driving a vespa pk (xl1) with a DR75 cylinderkit and a standard 16/10 carburator. the main jet at the moment is 55. the exhaust is a Tecnigas chrome banana. the airfilter is from malossi but he doesn't drive like he has to drive. when I drive full throttle, he doesn't go straight, he holds in, normally it drives on the speedo 70km/h but then it falls back to 60km/u, back to 70km/u, back to 60/u... does anyone know what's the problem and which main jet I need? greetz, Cédric