Motorcycle Repair: Fuel supply, header tank, alse

Question
I have got a Gilera runner 50cc (1999) as a first bike for my son. The problem is that there is no fuel delivery upon trying to start the bike. It has a header tank for fuel that is supplied by the pump which appears to fill ok. Then there is a tap that requires a vacuum to be created (tube connected to carburetor) to allow a diaphragm in the tap to move letting the main fuel supply through. I have had the tap off and found that sucking on the vacuum side allows the fuel side to open and there is at least some suction from the carburetor tubing. Any ideas what the problem might be? I wonder if the fuel tap could still be faulty needing more pressure than is provided but when I suck on the tube it is ok. Any suggestions would be very welcome.
Thanks in advance
David

Answer
hello dave,
the fuel tap could still be bad but look on the carburator for the overflo line pass a small wire through ie to see if its clogged up . i had the same problem on my sons 125 suzuko the carbs overflow line was obstructed. try this if it doesnt work i will give you something alse to try i will look through my achrives to help more but believe this is all to it . ok good luck and keep riding .

P.s please dont forget to leave feeedback ,on my answer
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                      thanks and god bless,
                    mitch kruszynsky