Piaggio zip 70cc jetting problems

Hey, I am currently having problems with my piaggio zip, i have installed 70cc big bore kit, 21mm TNT carburettor, gianelli chrome exhaust, 4.5gram rollers.
I was told a 80 jet would be good idea as i am running with standard air box, i put 80 jet in fired the bike up took it for a run and would reach 60mph and cut out straight away and then wouldnt start for awhile, i am wondering if the jet is too big or too small? please help

 

You should really be trying with a bigger jet than what youn "think" is the correct one and go down in jet size until you find the correct one. Spark plug test at full throttle will help you figure that out.

You could potentially be damaging your engine by running lean if the jet is the incorrect one.

 

Thanks for your response, i have tryed bigger jets and seems to be running way to rich so i have gone down in size and put 75 jet in and still cuts out on full throttle, recon i should go lower?

When changing 50cc to 70cc the jet increase is aroun 10%, 21mm carb around 5%, exhaust around 5%. Correct me if i am wrong. So working out, i should be running around 70 jet? would this help solve the problem?

 

As long as you do full throttle sparkplug check you dont really risk anything. Never really like percentages as they are only theoritical. Keep going until full throttle works then adjust the rest of the carb.

Remember as well to take the choke off is it is an automatic one

 

Thanks for the help i need to go buy a box of jets as lowest size i got i 75 and still dies on full throttle. The carburetor is a cable choke