140 running rich....

Farmall Super A, AV, 100, 130, & 140 1939 - 1973
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140 running rich....

Postby tnfirstfarmall140 » Sun Mar 27, 2022 10:45 am

Hey guys,

My 77 140 is generating just a little black smoke at idle. I rebuilt the carb (nothing really bad inside), replaced the points (adjusted a couple of times -right on the money for start, run and idle now), changed plugs (Champion), wires and rotor as well.
As soon as you crack the throttle, smoke goes away and runs strong. Interestingly, this does not create any burden at idle -still smooth, but cannot seem to make an impact with the idle screw and the rich run at idle. My carb is the Schlebler with only the idle mix screw adjustment, everything else is non adjustable.
Would really appreciate your thoughts and experiences as always.
Thanks for reading.

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Re: 140 running rich....

Postby SamsFarm » Sun Mar 27, 2022 11:09 am

Just a thought, but maybe it is burning a little oil from somewhere
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Re: 140 running rich....

Postby tst » Sun Mar 27, 2022 11:33 am

are the advance weights free in the distributor to work ?

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Re: 140 running rich....

Postby Don McCombs » Sun Mar 27, 2022 11:35 am

We hear a lot of reports of tractors running rich recently. By recently, I mean the last 5 to 8 years. I don't have any science to back this up and may be way off base with this theory. I'm wondering if ethanol fuel could be contributing to this phenomenon. I'd be interested to hear what others think and why.
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Re: 140 running rich....

Postby Jim Becker » Sun Mar 27, 2022 12:02 pm

Actually, ethanol makes a carburetor run lean. Alcohol requires a fuel to air ratio slightly higher than straight gasoline.

I think a lot the problem is from people "fixing" their tractors. A tractor doesn't run right, or not at all. It may be the product of sitting unused for a long time. Whether the problem was fuel related or not, the owner decides to clean or "rebuild" the carburetor. Wanting to be thorough, they run some metal object through all the passages to clean them out. The thing they use could be a torch tip cleaner or similarly abusive tool. The passages being cleaned probably include the jets, which have now been enlarged from the original size. The enlarged jets make it run rich. They now decide ethanol in the gas is causing the problem. So they start using ethanol free gas which just makes it worse.

Yes, I actually do see people suggest using torch tip cleaners on the internet on a regular basis. I've gotten tired of posting warnings.

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Re: 140 running rich....

Postby Rick Spivey » Sun Mar 27, 2022 7:24 pm

Just in case, I believe you will find very small passages around the throttle butterfly plate. Those passages are some of the ones Jim is referring to. They need to be open fully, and I use a combination of carburetor cleaner and a telephone copper wire. Ensure these passages are clean.
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Re: 140 running rich....

Postby tnfirstfarmall140 » Sun Mar 27, 2022 7:44 pm

Appreciate the feedback as always.

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Re: 140 running rich....

Postby ShawnAgne » Sun Mar 27, 2022 7:58 pm

Being a guy that always worried about stuff when I got my Cub and then my 300 I always wanted to "fix" stuff. In hindsight if it runs fine then I wouldn't worry about it, now looking good is another subject. I know with my tractors rarely do they get worked hard enough to get the motors hot enough and I'm sure this causes some issues. Well ok the Cub works hard cause its a Cub and a 5' deck, but the 100 and 300 don't. I've just come to realize hey they are 70+ year old tractors if they work fine great let it go and don't worry about it. My 100 is similar to what you are saying it smokes at idle but as soon as I run it up its fine. Carb was rebuilt when I restored it and still does the same thing. But the darn thing runs strong now. Personally like I said if its running I wouldn't worry about it.
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Re: 140 running rich....

Postby inairam » Sat Apr 09, 2022 6:05 am

Is it running rich at start-up or after it is warm? The Zenith carbs in general and particularly on the 140 do not like the cold.

Like Shawn said at some point they do run well if not perfect.
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