The screw at the bottom facing forward is the "high speed mixture" screw.
The one above it and at an angle is the "idle mixture screw"
The the highest one and facing outward is the "idle speed" screw.
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To set the carb (assumes the carb is totally out of adjustment):
1 - Turn both mixture screws all the way in (but don't force them tight...). Now open the idle mix screw 1 turn and the high speed mix screw 2 - 3 turns. Leave the idle speed screw alone for now.
2 - Set the throttle about 1/3 open and start the engine. Let it run for a few minutes to warm.
3 - Make sure the choke is open fully. If the engine stumbles when the choke is opened, open (turn CCW) the high speed mix screw until the engine runs steady.
4 - Set the throttle to idle (handle all the way forward) then adjust the idle speed screw in or out to set the idle RPM you want. Now adjust the idle mix screw in/out until you find the smoothest idle. If the engine now idles too fast, turn the idle speed screw as required to slow it back down. Then adjust the idle speed screw once again to get the smoothest idle.
5 - To set the high speed screw, run the engine at full throttle and adjust the screw in/out until the engine runs fastest/smoothest. Then give it an additional 1/8 to 1/4 turn open (CCW).
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Note on the two mixture screws: The idle mix screw turns in (CW) and the high speed turns out (CCW) to give a richer mixture.
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Today's Featured Article - Good As New - by Bill Goodwin. In the summer of 1995, my father, Russ Goodwin, and I acquired the 1945 Farmall B that my grandfather used as an overseer on a farm in Waynesboro, Georgia. After my grandfather’s death in 1955, J.P. Rollins, son of the landowner, used the tractor. In the winter 1985, while in his possession the engine block cracked and was unrepairable. He had told my father
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