I have a 2001 Yamaha Aerox that i have just bought, not in the best conditions if im honest but it starts, it can rev sometimes but not enough for it to move, it has a 70 kit fitted at some point and a doppler exhaust, 4.9g rollers, 21mm carb with size 86 main jet but im not sure what else, ive cleaned out the carb and jets and pit in some fresh oil. Could anyone please help me!!

treat it to a new plug for christmas.

re-clean the carb ,just in case you missed something.

Or , your coils breaking down ,under load...maybe.