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H Carb problem?

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Stevishere

11-21-2007 04:12:25

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I just rebuilt the carb on my gas H (1940). It now idles great. When I adjust the main fuel adjustment screw ( the one on the upper left of the carb)it has no effect. As the manual suggests, I set it 3 turns out. To adjust, it says to accelerate full throttle and turn the screw in to lean until the engine starves out then back off just until smooth.
I can turn the screw all of the way in until it bottoms out with no change, same with backing it off.
Any ideas?
Also, under load, it runs very rough, ready to stall.

I greatly appreciate any ideas anyone has.

Thanks!

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Michael Soldan

11-21-2007 07:49:05

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Re: H Carb problem? in reply to Stevishere, 11-21-2007 04:12:25

If you have made the proper setting on the carb it is a float problem that needs to be set .

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Stevishere

11-21-2007 10:18:14

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Re: H Carb problem? in reply to Michael Soldan, 11-21-2007 07:49:05

I verified that I have set the float at 1-27/32 from the highest point on the float to the gasket face of the upper half of the carb (when it is upside down).
I noticed my float was slightly disfigured, possible from water freezing in the bowl at some point? Would this have a detrimental effect on the float's operation?

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Michael Soldan

11-21-2007 11:48:55

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Re: H Carb problem? in reply to Stevishere, 11-21-2007 10:18:14

Steve, it could...also is the float good in that it has not sprung a leak and gasoline is filling it. We had a '29 Chev we were restoring and we couldn't make it run right until we discovered a pin hole in the float, she ran good after that.

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RustyFarmall

11-21-2007 05:37:42

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Re: H Carb problem? in reply to Stevishere, 11-21-2007 04:12:25

The screw on the upper left is the idle air adjustment. It is supposed to be set at 1 1/2 turns out, and then adjusted after the engine is warmed up. The load, or high idle adjustment screw is the one at the very bottom of the carb. It is the the one that is set at 3 turns out, and very rarely will need any further adjustment.

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Stevishere

11-21-2007 10:21:27

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Re: H Carb problem? in reply to RustyFarmall, 11-21-2007 05:37:42

I checked my manual and it says just the opposite.
I have an H with HC Gas engine. It has the disc style float. I was able to smooth the idle out very well with the bottom angled screw. I won't run with the bottom screw out 3 turns. It coughs and gags.
Do I have the wrong manual?

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riverbend

11-21-2007 11:42:35

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Re: H Carb problem? in reply to Stevishere, 11-21-2007 10:21:27

If the carb is for an H it will have a little round brass tag rivitted on near where the shaft comes over from the governor. The tag will say something like 45108 DB (kerosene, gas will be similar but different). If it does have the tag and has those numbers on it, it is an H carb. The adjustment screw on the upper left (facing the carb) is an idle air adjustment screw.

You can check for yourself. Take the carb apart and see if that screw controls the amount of air that comes from behind the venturi and goes up to a slot by the throttle plate. The main jet is in a well under the float chamber.

Greg

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RustyFarmall

11-21-2007 11:39:45

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Re: H Carb problem? in reply to Stevishere, 11-21-2007 10:21:27

I don't know what manual you are looking at, but I do know which adjustment screw is which. I've rebuilt enough H carbs that I don't even look at the manual anymore.

Also, you mention that the float is disfigured. That alone will not cause problems, but usually when a float is disfigured it will also have a hole in it, and then it will not float, which is causing your over-rich problems.

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City-Boy McCoy

11-21-2007 04:42:18

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Re: H Carb problem? in reply to Stevishere, 11-21-2007 04:12:25

Stevishere: It sounds like you may not have let it soak submerged long enough in some powerful carb cleaner. If so, some passages may still be blocked or partially blocked. Make sure you blow all the little passages out good with some strong air pressure. Also, I suggest getting some thin wire and run it through some of the passages to make sure they are clear.
When it runs rough under load, is it making black smoke? If so, it is too rich. If not, and if it is popping while running rough, it is too lean - again an indication some passage may not be clear.
What symptom did the tractor have that prompted you to rebuild the carb to begin with? In other words, are you sure you don't have another problem - say perhaps a vaccuum leak somewhere? Good luck
mike durhan

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Stevishere

11-21-2007 05:36:16

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Re: H Carb problem? in reply to City-Boy McCoy, 11-21-2007 04:42:18

When I bought the tractor a year ago, it had been used infrequently over the last 20 years as it is a 1940 that I purchased from the original owner. The tractor had been "gone over" by a friend of his and ran pretty well, as long as the choke was closed about half way.
I initially rebuilt it without using a dip cleaner or compressed air. It still had the same issue. I just rebuilt it again (with another new rebuild kit) and this time, I soaked it in Chem-Dip carb cleaner for 2 days, then cleaned out all holes, etc and used compress air in all areas.

It started right up, the choke works as it should now, I just have the load issue and no effect on the leaning, lean or rich.

Good idea on the vacuum leak, I will check, though I don"t know of many places that can happen except manifold to head or carb to manifold. Am I missing any?

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