Farmall M Carb Settings? (2024)

It should only have 2 screws on it. The high one is the idle screw and you turn it in to make it richer but a start point on it is about 1.5 turns out from bottom. The lower one is the main jet and it should be around 4 or 5 turns out form bottom. The make it leaner you screw that main jet screw in a tad just till the black smoke stops and you should have it about right

that third top screw is for the idle throttle stop.set engine idle to approx.425 rpm with this screw. a good # is 3 turns out for the btm.main adjusting screw. middle idle adjusting screw is 1 turn out and your very close. i set them as this after o/h and dont really hardly need to readjust.if your out in field plowing or working hard then may need to open the main 1/2 turn.

Thanks for the replies. I bought a carb rebuild kit today and it recommended the screw settings (they were pretty similar to what you guys had suggested) and it ran decent, but if you throttled it up too fast it would pop. My uncle played with the screws while I revved it and we seemed to have gotten it pretty smooth. Pulled the plugs out and they're as black and carboned as can be (probably from it running rich and smoking like a diesel last night when the carb was all screwed up) So I'm going to pick up a set of plugs, and put an in-line fuel filter on it when I get off work, and see if it runs any better.

Watch out about putting an in line filter in these gravity fuel systems. Most in line filters are meant to be used with a fuel pump, and some of them can actually cause a restriction. The screen in the sediment bowl and the screen in the inlet fitting in the carburetor are all the filtering you need.

Take a look at your oil bath air cleaner and make sure the oil level isn't too high in the cup. I had that problem on my Super C and I experienced similar problems. The in-line filter I installed caused more problems then it cured mainly fuel wouldn't flow when the tank was down a few gallons as there wasn't enoung head presure in the fuel level. Good luck and hope it is a simple fix for you, Hal.

Ah, I thought it was for other reasons. Ive always valued your advice here and there, although I havent always agreed with it. I just dont think Jr would have booted you for giving good advice. If I recall, something similar happened here a while back to someone else who wouldnt stop what he was doing even after being asked by the owner(s).