adjusting H Farmall carb

Farmallb

Well-known Member
Had to get a new er top for the carb. Got it back from the mechanic today. Ive had it on and off 3 times now. It dosnt run right. It dosnt idle, and it DOES race. Im 70, and ive forgotten which screws do what, other then the idle adjustment screw, which comes out from the top straight outward. Ive adjusted it in and out to no good response. Which way idles the engine down, going in or going out? Which what do the other 2 screws do. I know one is air and one is fuel. Im assuming the one set at an angle at the bottom is air, and the one set near the butterfly is fuel. Am I right?
What is a good starting setting for air and gas. 3/ 3 1/2 turns from inside out?
 
Are you sure you have the tang from the governor in the groove of the opening on the front of the carb? Just sounds like you don't.
 
very bottom screw is fuel-out about 2-3 turns. Screw straight out is gov.idle speed w/throttle in idle position{approx. 500 rpm} other screw is air and turn which ever way it runs the smoothest at idle.

My way.
 
I took it off twice today. Even put on my reading glasses to stab the tang into the slot. Ill try it again tomorrow.
 
(quoted from post at 13:51:48 11/20/17) very bottom screw is fuel-out about 2-3 turns. Screw straight out is gov.idle speed w/throttle in idle position{approx. 500 rpm} other screw is air and turn which ever way it runs the smoothest at idle.

My way.

Initial setting for the air-idle adjustment screw is 1 1/2 turns out. May need slight adjustment after the engine is warm.
 
Here's my procedure I compiled from several manuals;
Make sure the float isn?t sticking or touching the insides of the float chamber. Some previous advice was to use a Dremel tool and smooth the insides of the float chamber so the float doesn?t rub or touch. Pretty important.
Set the float so the top of it rests 1 27/32" above the flat surface of the float chamber.
[Note a new float might already be set correctly.]

INITIAL settings are as follows to get the engine started;
Main fuel adjusting screw; big screw facing down at an angle, towards the rear, at the bottom of the carb; 2 1/2 to 3 turns open. This main screw turns clock-wise for leaner mixture. [This screw adjusts fuel.]
Idle-air-mixture screw; smaller screw facing forwards, on upper left-hand side of carb; 1 to 1 1/2 turns open. This idle screw turns counter-clockwise for leaner. [This screw adjusts air.]
Idle speed screw; faces outboard, at the top of the carb; set for 450 rpm, and make sure the governor correctly engages in the slot. [This screw adjusts RPM?s.]

FINAL settings are as follows;
Get the engine warmed up, and idling.
Turn OUT the small idle-air-mixture screw until rough running, then turn in until engine idles smooth. (Mine is set at 1 turn open.)
Rev it up, wide open, warmed up, then turn the big main fuel adjusting screw IN until rough, then out til smooth, then 1/4 turn to 1/2 turn further out. (Mine is set at 1 turn open. Other advice has been to set it at 2 1/2 turns open for pulling implements.)

Engine should rev up smoothly and evenly.
Too Lean = stumble, sputter, damaged melted plugs.
Correct = tan plugs.
Too Rich = back smoke, black sooty plugs.
 
For what it's worth be careful turning the mixture all the way to bottom. There is a very small brass jet that will split if turned too far and finding a new jet is tough. Do not ask how I know.
 

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