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Farmall M Carburetter Setup

32664 Views 13 Replies 4 Participants Last post by  John M
Hi All
I posted this earlier but didn't get a chance to record the replies :(
Can somebody throw some light onto which screws do what?....!

A.
B.
C.
D. Fuel drain tap
E. Choke
F. (possible flooding drain unit for air intake) but I have no idea how this drain fuel which ends up in the air intake
G. Fuel-in (from tank)

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A is idling speed
B is idling air mixture..the further in you screw it the richer the mixture
C is the main jet, the further in you screw the main jet, the leaner it becomes.
To get the thing to run, you usually have them both 2 1/2 to 3 turns out from the stop.
Adjust the main jet first at 3/4 throttle, then do the idle one at about 700 revs/
Fine tune it from there, every motor is different.
Let me add (again), you should set the idle mixture, B, by closing (in) until it smokes lightly, then turn out slowly until it clears up. C can be anywhere from 1/4 turn out to 5 turns, just set a 3 and adjust for your needs.
That's great - thanks both.
I'll try these out and see how I get on.

Any ideas how the air supply flooding valve operates? From what I can see inside the float chamber its just a hollow tube fitted to the base of the float chamber. Pretty sure it doesn't work as I always get lots of fuel backing up in the air intake pipe. :?
badgo said:
That's great - thanks both.
I'll try these out and see how I get on.

Any ideas how the air supply flooding valve operates? From what I can see inside the float chamber its just a hollow tube fitted to the base of the float chamber. Pretty sure it doesn't work as I always get lots of fuel backing up in the air intake pipe. :?
If your getting fuel in the intake, you are eother choking too much when trying to strat it, or your float is set too high. Only moving part insdie that carb is the choke butterfly, and the idle/engine speed butterfly.
Still trying to perfect the set up...

It seems to have a habit of firing a couple of times then giving up. Those couple of rotations seem to be enough to draw fuel in and flood itself.

I'll keep tinkering though!
They require very little choke. It's easy to flood 'em if you're not careful. Most of the time unless it real cold I've found I can pull the choke out at the instant I hit the start pedal and push it back in one smooth motion and she'll take right off. If it's cool I may have to "feather" the choke for a minute, but usually not.
You make it sound easy!

I probably need to point out mines a crank start and was never fitted with an electrical pack. Boo!
Crank start? Granted I don't crank start my "M" but I do my Cub. Irregardless of the physical demand of starting, this is how it works on the mag equipped Cub.

Ignition switch off, fuel on, choke closed, open throttle 2/3...crank her twice. Flip the butterfly open on the choke, turned the ignition switch on, crank her one more time. 8 times outta 10 she'll go...

Notice I was honest, 8 times not 9, not 10 :)
Its actaully easier to NOT flood one when cranking with the handcrank. On my Ms, I turn on the gas, then pull the choke rod out, pull up on the crank 3 times, then pull out the switch, push in the choke rod and she usually fires the first pull. Or at least thats how I use to do it, havent done it in years! Would it be possible for you to belt it up to another tractor?
How do you mean 'belt it up' ?

I have a TE20 which is a reliable runner....

The M will start with a tow no problem - but I kind of consider that cheating ;)
badgo said:
How do you mean 'belt it up' ?

I have a TE20 which is a reliable runner....

The M will start with a tow no problem - but I kind of consider that cheating ;)

Using another tractor with a belt pulley, and assuming you have one on the M as well, you can run a flat belt from the runner to the M, in short "pullling it off" with the belt pulley attachment.
Ahh - I see.
No it doesn't have a pulley. I've been looking for one though - don't suppose you know if the stud pattern is universal (eg - would a fordson of similar gae fit?)
badgo said:
Ahh - I see.
No it doesn't have a pulley. I've been looking for one though - don't suppose you know if the stud pattern is universal (eg - would a fordson of similar gae fit?)
No I dont, never really thought that much about!
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