You may need to re-jet the carburetor. There there different main jet that readily available for the genny. .92 , .95, and .98 mm. If not one of these then it is time to pull out the micro bits. But first try increasing the idle mixture slightly. It can affect the overall mixture at times.
Also the output should be closer to 120-130 vac @ 60-62 Hz (3600-3750 rpm). My current household voltage is 130 vac here.
BTW I going need to get the ruler out and slap your hand for the MTF thread. Just kidding....