H Main adjusting screw not working.

IHplankton · Jul 10, 2015

I just received my new main adjusting screw for the carburetor on my H today and put it in. The needle is really tight to turn I can only do it with a screwdriver but I put it as close to 3 turns out as I could (hard to tell when it has slight resistance since it has resistance all the time both in and out) and it fired right up and sounded pretty good. Note: there was nothing wrong with tractor operation before this I just had a completely stripped and leaking packing nut.

I ran around a field with a disc real quick to warm it up and then went to do some fine tuning. However much to my surprise the screw does nothing to how it runs I can turn it all the way in or almost all the way out and the engine doesn't change....but it is running pretty good right now so maybe I'll just leave it just thought to see if anyone on here had an idea how that is even possible I would obviously like to be able to tune it better/open it up a little for plowing etc...

pete 23 · Jul 10, 2015

Most likely you have a fixed main jet that is calibrated for full load unless you have a carburetor for distillate. Even then, most of them over the years have been changed out for gasoline. When you have a calibrated fixed jet you cannot increase the fuel to excess no matter how many turns you screw it out. Now, on the other end, screwing it in should kill the engine, BUT, many needle are not long enough to shut the main jet off, OR , there is so much packing the needle cannot screw in far enough. You can see that problem if you have the carburetor apart but not from the outside. I would not worry about it and keep it in mind when you have to clean the carburetor again and then take a look unless you feel it is burning too much fuel for the job you are doing. I see very few H & M's that you can give them too much fuel by turning the screw out, contrary to popular opinion.

rustyfarmall · Jul 10, 2015

(quoted from post at 10:35:40 07/10/15) I just received my new main adjusting screw for the carburetor on my H today and put it in. The needle is really tight to turn I can only do it with a screwdriver but I put it as close to 3 turns out as I could (hard to tell when it has slight resistance since it has resistance all the time both in and out) and it fired right up and sounded pretty good. Note: there was nothing wrong with tractor operation before this I just had a completely stripped and leaking packing nut.

I ran around a field with a disc real quick to warm it up and then went to do some fine tuning. However much to my surprise the screw does nothing to how it runs I can turn it all the way in or almost all the way out and the engine doesn't change....but it is running pretty good right now so maybe I'll just leave it just thought to see if anyone on here had an idea how that is even possible I would obviously like to be able to tune it better/open it up a little for plowing etc...

You WON'T notice any difference UNTIL the tractor is working hard. Screw it in until it is open only about one turn, and THEN drop the plow in the ground. The ol' girl should start sputtering like it is running out of gas almost immediately.

IHplankton · Jul 10, 2015

Interesting, I bet there is too much packing preventing the needle from turning in far enough to kill the engine. The packing that the needle came with is twice the amount that it had before.

The tractor was originally distillate but Im not sure if its the original carburetor or not. before I changed the needle I could mess with it and hear the difference with it running at WOT I could get it to almost die out turning out and in too far. Thats why I was surprised at this new needle.

I wont worry about it I guess then, all she needs to do from now until fall is run a sickle and a rake.

rustyfarmall · Jul 10, 2015

(quoted from post at 12:54:34 07/10/15) Interesting, I bet there is too much packing preventing the needle from turning in far enough to kill the engine. The packing that the needle came with is twice the amount that it had before.

The tractor was originally distillate but Im not sure if its the original carburetor or not. before I changed the needle I could mess with it and hear the difference with it running at WOT I could get it to almost die out turning out and in too far. Thats why I was surprised at this new needle.

I wont worry about it I guess then, all she needs to do from now until fall is run a sickle and a rake.

I find it much easier to loosen the packing nut just a wee bit, turn the screw to where you want it to be, and then retighten the packing nut.

I have encountered a couple of H carburetors that due to a manufacturing glitch, or whatever, would not accept the full packing. Only solution is to slip the packing onto the screw and then use a razor blade to whittle away part of the packing. Trial and error until it fits.

Russ from MN · Jul 10, 2015

We have a C that is making oil, and the hydraulic pump is not leaking, so I assume that it is running too rich. But it runs so well that I don't want to mess with it until the parade season is over! It has fairly fresh 15-40 in it and has good oil pressure, and when I drain our the excess it will not light with a match, any ideas?

rustyfarmall · Jul 12, 2015

(quoted from post at 16:15:17 07/10/15) We have a C that is making oil, and the hydraulic pump is not leaking, so I assume that it is running too rich. But it runs so well that I don't want to mess with it until the parade season is over! It has fairly fresh 15-40 in it and has good oil pressure, and when I drain our the excess it will not light with a match, any ideas?

If it was a fuel issue, the tractor would NOT run that good. Are you sure it is not anti-freeze getting into the oil?

H Main adjusting screw not working.

IHplankton

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pete 23

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rustyfarmall

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IHplankton

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rustyfarmall

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Russ from MN

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rustyfarmall

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