My bet is that's an H70-130210D. If that's the one, there will be a main (high speed) adjustment screw on the bottom, an idle mixture screw on the side, and an idle crack screw on top that prevents the throttle plate from fully closing.
Let's go through an adjustment procedure as well after you verify the jet.
Start with the main screw underneath the carburetor set at 1-1/2 turns from gently seated. Do not overtighten. Start with the idle screw on the side at 1 turn.
Start the engine and let it warm up to operating temperature, usually about 3-5 minutes.
Move the throttle to full speed. Start with the main screw and turn it in 1/8 turn at a time, give the engine a few moments to adjust to the new mixture at each stop, and note the position of the screw when the engine starts to sputter.
Now turn it out in 1/8 turns just like before and fine the other point at which the engine starts to sputter.
Set it halfway between the two points.
Now bring the throttle down to idle and do the same thing with the idle screw.
If further adjustment is required, the main adjustment should be made with a load on the engine. Engage the auger. If the engine stops or hesitates, turn the main mixture adjusting screw out 1/8 turn at a time, testing each setting, until it engages properly.
If the engine smokes excessively, turn the main adjusting screw in 1/8 turn at a time, testing each setting under load, until this condition is corrected.
After the main mixture is set, move the throttle to the idle position. If the engine does not idle smoothly, turn the idle mixture screw 1/8 turn either in or out until it engine idles smoothly.
Did you clean off the carbon in the head and inspect the valves for proper seating? Do you have a compression gauge to take a cylinder reading by any chance?
Let me know and we'll continue.
Edited by Rick on 12/2/2010 at 10:05 PM EST