Got the Honda GX31 running tonight. Have not made the complete header yet but ran it anyway. Put an 18/8 Master Airscrew wood prop on it. Fired right up and purred like a kitten. Had to back the high needle out about 3 turns to get it to wind up. Runs right up to high RPM then just snaps right back to a perfect idle. I will experiment with bigger carb tomorrow. I have several 11.11mm. Could not get a tach reading as the lights were messing with the strobe. Ran it for 20 minutes on less than 8 ounces of gas.