hi,
to me it sounds like the little fule filter in the tank is dirty and bloked. i say this becuase at 1/2 or full choke here is going to be allot more suction on the fule line as opposed to no choke, if that makes sence.
and i have pulled probley 20 zamma / walbro carbys appart and never once have i replaced any of the gaskets (need to be so careful when dismantleing!!)
hope this sheds some light on the situation
