Power valve circuit does'nt come into play @ idle , the PV channel will only flow fuel when main metering starts , is this a new carb out the box? , is the PV gasket in tact/PV blown , is the motor idling on the mains? (trans slot too far exposed) , float level set to high? , N&S seating ok? , too much fuel pressure? , timing too far retarded @ idle? IABs blocked, pump umbrella seals?