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sglick

Farmall M Carburator

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Does anyone know the base setting on a M carb. Thanks Scott <_<<_<

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Does anyone know the base setting on a M carb. Thanks Scott <_<<_<

Idle mixture screw 1 1/2 turns out. Load adjustment screw 3 turns out.

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Does anyone know the base setting on a M carb. Thanks Scott <_<<_<

Idle mixture screw 1 1/2 turns out. Load adjustment screw 3 turns out.

I'm working on a 400 and was wondering about the settings. Which is the load setting screw? She used to never idle low enough until I fixed the slop in the throttle linkage and pushed down the governor shaft tube. However the uppermost screw, I'm assuming the idle screw, doesn't respond unless you tighten it. Is the pin/buttlerfly worn out? I'm tempted to put an overhaul kit in it.

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The load setting screw is on the bottom...

A good carb kit would be money well spent...

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A good carb kit would be money well spent...

Be sure to get a good quality kit that is complete. I have had bad luck with the Tractor Supply kits. You should get a throttle shaft and choke shaft in the kit, along with the bushings that the shafts ride in. Belive it or not air can get sucked by the shafts effecting the mixture and make the engine run poorly.

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3 turns out and 1 1/2 turns out...from all the way in right? I'm a little leery of doing that because a mechanic said to be careful with older stuff. I've noticed every now and then the carb will leak a little gas after running the engine for a few minutes. It also seems when I was mowing last summer she was burning alot more gas than normal. Yes, a carb kit is in order. One website is selling a kit for $19. Too good to be true?

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3 turns out and 1 1/2 turns out...from all the way in right? I'm a little leery of doing that because a mechanic said to be careful with older stuff. I've noticed every now and then the carb will leak a little gas after running the engine for a few minutes. It also seems when I was mowing last summer she was burning alot more gas than normal. Yes, a carb kit is in order. One website is selling a kit for $19. Too good to be true?

Those are good starting points. epending on the load you are going to be turning 3 turns on the load screw may be a little lean. I usually set mine at 4 turns. After running the tractor underload for a while pull a sparkplug & see what it looks like. If black & sooty turn the load screw in 1/2 - 1 turn, if whitesh gray turn it out 1/2 turn or so.

Adjust the idle screw to where you want the engine to idle. I set mine to idle fairly slow, can't tell you where, it's just an "ear" thing. After setting the idle there is another screw to the right of the idle adjustment screw. It's an air screw & needs to be set so the tractor idles smoothly.. Usually a quarter turn one way or the other after getting your engine idle set will do it.

As for running the adjustment screws in, that's the only way where your going to have a known starting point & is the way the book calls to do it. Just don't go tightening the adjustment screws down tight with force whn bottoming them out against their seats. Turn them in till you feel them just start to contact the seat then turn out from there.

$19 for a carb kit is about as low priced as I have seen. Last one I bought was arund $25. I usually buy a "Tisco" repair kit at my CIH dealer. First thing I do after buying the Tisco is to throw their needle valve away & buy a CIH one. Every aftermarket needle valve I have boughten wants to stick. Don't have near the problems with the CIH ones. I wish they wuld come back out with the ones with the steel tips like they originally had instead of the rubber tip. BTW, you can buy a carb kit from CIH but the last time I checked it was over $100 :o However, it does have a lot more pieces than the aftermarket kits but the aftermarkets usually will have the basics that you need.

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Thanks boog. The reason I'm needing a carb kit is because the idle screw doesn't respond when I'm backing it out...only when I tighten it and the engine speeds up. That happens with the screw almost all the way in. I did push down the governor shaft tube which reduced the idle. The governor shaft adjustment is maxed out; it's been threaded all the way down. All in all the tractor is solid. She just has alot of small issues from the previous owner...like the fence spike I found which was connecting the throttle lever to the shaft. It had wallowed out so I filled in the holes with weld and re-drilled. Almost all the slop in the throttle has been fixed whereas before you could move the throttle 1/4 from idle with no response.

Looks like I have some adjustments in order.

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