OK My reference says it's a Tecumseh HM90 engine.
There should be 2 adjustment screws on the carb. The main mixture screw is on the bottom of the float bowl, and the idle mixture screw is on the side of the carb.
Turn both screws in until they just seat, not too tight or you'll ruin the needles! Then back them both out 1-1/2 turns. Start the engine and let it warm up for at least 3 minutes. Start with the main mixture screw. (Bottom of the float bowl) With the throttle set on high, slowly turn the main screw in until the engine starts to run rough, Then slowly turn it out, counting the turns, until it starts to run rough again. Then turn it back in half way between the lean and rich settings.
Now set the throttle on low, and repete the above, only this time turning the idle mixture screw on the side of the carb.
That should have it.
Rick
November 2005