having some troubles :/

hi all i dont know much about bikes, so ill try to tell it how it is.

My aprilia rs 125 53 plate starts and ticks over great, but wen i rev it. when i twist the accelerator nothing happens then it does.
(sometimes its dies on me) , we have check all the pipes and look ok?
it sound like its pulling in air some where. or could it be the coil?
i have drian the tank and clean fuel in.
new plug.

my bother inlaw took carb off and cleaned reset it.

thanks