you have done a good job of diagnosing so far. clearly there is some blockage of the fuel between the tank and the combubstion chamber. First place to look is the needle valve. Unscrew the needle valve completely and try to see if there is some dirt or something blocking the passage of fuel thru the NV assembly. Sometimes a very small diameter wire can be used to clean out the fuel passage. This engine relies on a reed valve to allow fuel to suck in to the crankcase. the reed may be malfunctioning. thr reed is a very thin metal between the integral tank and the crankcase.