What to change that my aerox would have more torque

Hi, i have Yamaha aerox that wheels up pretty easily at 10km/h it revs up and then it lose about 1k rpms and the torque, after that and catches up at almost 60km/h what should i change in my setup? The setup is:
DR 70cc
17,5 dellorto 88 jet
Malossi e5 air filter
Carenzi crank
Malossi multivar 3 4,7 gram rollers 3 7,3 gram rollers
Giannelli Extra v2 exhaust
Malossi x-kevlar
Stock clutch with i dont know which brand green clutch springs
Jasil yellow spring

Max speed ~80km/h
I don't know what to change but i would like it to be slow at the start but to have much more acceleration from 20km/h to max speed. Anything helps.

 

Hi, it's me again, change the rollers to 3 5,5 grams and 3 4,5 grams it runs much better and picks up much more rpms but the max speed decreased to 70km/h and i don't think that dr70 kit should go only 70km/h? any ideas how to make it faster? is it becouse the pipe is too "weak"?