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Farmall M Carb - Adjustment or More?

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Clarkbug

03-10-2008 15:27:11

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Hello All.

I just wanted a little sanity check on what I was thinking, so I wanted to run it by every one.

My '49 M had the carb re-built about a year and a half ago, with not too many hours since the rebuild. However, it really doesnt like to idle much at all, unless I pull the choke most of the way out.
That to me says that the carb is just running lean, and I need to just adjust things like the manual/shop manual says. (Im not entirely sure how this will work since they say to do it with the choke off, but Ill figure it out I suppose)

So is just a carb adjustment all that I should be needing? Or is there a deeper problem going on here? Im about 400 miles away from my tractor right now, so I wanted to get any parts I would need ahead of time.

Thanks in advance!

~Bug

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Clarkbug

03-11-2008 15:23:58

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Re: Farmall M Carb - Adjustment or More? in reply to Clarkbug, 03-10-2008 15:27:11

Sometimes the carb does leak if I dont remember to turn the gas off, but that was before I flushed everything out of it. Could that potentially be a float issue, or is that just the seating of the needle valve?

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Janicholson

03-11-2008 15:35:33

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Re: Farmall M Carb - Adjustment or More? in reply to Clarkbug, 03-11-2008 15:23:58

If it is sometimes, it is seating, and even a piece of hair in the valve. If the float is dry, you can shake it and it will be quiet inside. If it is heavy, or has liquid noise in it it leaks. Careful Soldering can repair all but the worst cracked floats, JimN

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Daniel Henebry

03-11-2008 05:50:56

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Re: Farmall M Carb - Adjustment or More? in reply to Clarkbug, 03-10-2008 15:27:11

Everyone has good suggestions, but I would check the float in the carb. They can get fuel in them after time and make them too heavy to get the bowl full thus causing the same symptoms you are having. A few drops of fuel or condensation in the float can screw it up big time. I had this on several small engines and my H.

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Janicholson

03-11-2008 06:30:35

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Re: Farmall M Carb - Adjustment or More? in reply to Daniel Henebry, 03-11-2008 05:50:56

Daniel. Not being critical, just correct, but a sinking float allows more gas into the carb. The more it weighs the higher the fuel level, until the fuel runs over the high speed jet height and or out the bowl gasket. I've been there so many times that there is no doubt. JimN

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Clarkbug

03-10-2008 19:19:02

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Re: Farmall M Carb - Adjustment or More? in reply to Clarkbug, 03-10-2008 15:27:11

Thanks for all the thoughts everyone.

Im pretty sure it was a high quality rebuild kit that went into it. The gent I bought it from spent several hours talking my ear off about the tractor, telling me all the things, good and bad, that he knew about. I guess he paid one of the "local legends" of rebuilding to take care of the carb for him, and used one of the high quality kits after putting too many of the cheap ones through it.

However, I do know that I had some rust in my tank, after fighting with it in my sediment bowl for a few starts. I had to pull the drain on the bottom of the carb to get it to start once, and got all sorts of goodies out when I did that... But the sediment bowl is now clean, the tank is clean, and a new fuel line has been put in.
Based on what everyone here has said so far, it sounds like some of that crud might be plugging up a jet in the carb somewhere, or I have an air leak going on. I dont think my manifold has a hole in it or isnt sealed properly, but Ill check with the torch to see. (I do know if I put my hand near it, I can feel exhaust blowing through two holes in the manifold...but Im assuming this is normal...)
Ill see what I can discover this next trip home, thanks for all the ideas!
Ill post back to let everyone know how it went, or if I need more ideas.
Thanks,

~Bug

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Janicholson

03-10-2008 17:12:09

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Re: Farmall M Carb - Adjustment or More? in reply to Clarkbug, 03-10-2008 15:27:11

Check first for a vacuum leak at the carb to manifold, in the manifold itself, or at the head to manifold gasket. Use a propane torch with the head off to allow raw propane to get into the leak areas, gaskets etc. Run the engine at the edge of not running (choke as far in as it will keep ticking over) then see if the propane will make it perk up. Do not use massive amounts, and do it outside.
If that does not produce results, I think a idle port has crud in it. Remove, assess, clean, and blow carb spray through every little passage. JimN

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Charlie M

03-10-2008 17:09:17

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Re: Farmall M Carb - Adjustment or More? in reply to Clarkbug, 03-10-2008 15:27:11

If runs OK with the choke out it could mean its sucking air somewhere that shouldn't be. Is the carb on tight and is there any cracks or holes in your manifold. It could be other things as already mentioned but these are freebies.

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Slappy

03-10-2008 16:29:08

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Re: Farmall M Carb - Adjustment or More? in reply to Clarkbug, 03-10-2008 15:27:11

Could be a lot of things and I'm certain that you will get lots of good ideas from all of the great guys and gals on this site - one of them will solve your problem.

Before I pulled the carb or bought an expensive kit though, I'd try the easy fixes first. One thing I would check, is if you are getting gas through the line. Plugged lines and rusty tanks are common. Also, if you have the means to do so, check the timing. It might have a plugged jet or port that could be fixed by disconnecting the air cleaner and spraying in some carb cleaner (watch out it will remove paint). If it is lean you would, I think, notice a difference if you let the main jet screw out.

If all the easy stuff fails, you may have to get it on the bench.

Good Luck and tell us what the problem was when you find it.

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james rumph

03-10-2008 15:51:12

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Re: Farmall M Carb - Adjustment or More? in reply to Clarkbug, 03-10-2008 15:27:11

If it was one of those cheap TSC rebuild kits that is probaly the problem. The cheap aftermarket kits are a joke.

It sounds like there is a air bleed plugged ! Take it apart and blow out all the holes real good. I ran into a problem like that and was told to get the cheap kit out of it.

I bought the factory rebuild kit and it runs great, but they cost .

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