Hi All I have owned a 2014 Vespa primavera 50cc 2 stroke since late 2020, i have recently done a full engine rebuild with new gaskets etc and installed a stage 6 mkII race 70cc cylinder kit, HPC crankshaft, 21mm dellorto phbg carb, manual choke, polini variator- 4g rollers, stronger clutch springs, and a roost rs5 exhaust (with some small dents), and it will not for the life of it move, it will idle fine (requires a bit of throttle with the choke pulled out) and when on the stand it will rev up to the max readable rpm (14000) however when on the ground it will rev to about 4000-5000rpm and will ever do slightly creep forward, any help appreciated, TIA
Fit all the original transmission and exhaust and try it, change one item at a time to find what piece is making a difference.
I recently tried taking it for a test ride after fitting lighter rollers and re jetting seemed to have a decent throttle response and be getting into the powerband easily on the stand, got up to about 10mph and just into the powerband before it began to backfire and lost all power, was able to keep the engine running with a little throttle but it had nowhere near the power it had before
