scooter hesutates on full throttle from stop. then picks up fine

i have a runner 50 carb version. my old dellorto 17.5 carb was shit so i got a new motoforce one. i have a yasuni r on stock cylinder with a prox piston. 62 main jet, modded air box. the ped hesitates ti rev from idle, and on full throttle it need its time to pick up but then it accelerates really well. it reaches almost 11k rpm. i had this problem since day one and it doesnt seem to go away. i was thinking downjetting one or two sizes as the bigger jets bog the bike. i installed carbon malossi reed petals and theres no big difference. any idea? maybe pilot jet?