Gilera runner carburettor problem

I have a Gilera runner 50 with:
DR Evo 70
Malossi multivar
Malossi fly clutch
RMS crank
Dellorto Phva 17.5 (70 main jet)
I cant turn on the bike when i have the airbox on. Ia have to take of the airbox turn it on hold the throttle and put on the airbox and when i release the throttle it turns of. The fuel from the carb is going in the airbox. What could be the problem. I have tried it with 2 carbs but i used the same needle, spring and the plastic part around the needle on both.