Too much fuel to carburetor

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calebpalmer86
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Too much fuel to carburetor

Postby calebpalmer86 » Thu Oct 29, 2020 7:15 pm

Before I post my inquiry, just wanted to say thanks for all the help in the past to everybody who has chimed in. Last time I posted, my inherited ‘50 Cub’s motor was locked up. This forum helped me be able to hear her run again for the first time since before my Paw Paw, who gave me this tractor, passed away, over 20 years ago. She sounds and smells just like I remember.

Here’s my new question. The engine runs and sounds perfect if I manually restrict the fuel coming into the carb using the stopcock on the gas tank. If I open it up all the way, the engine will either not run, or run very rough. Fuel will pour from the carb if it is not running. I assume this is a float problem from what I’ve read here and other places, but despite cleaning and rebuilding the carb twice (using all the original parts), I’ve made no progress. Would it be recommended to buy a full rebuild kit or is there something cheaper/easier that I could try first.

I’ll be posting another question or two also.

Thanks in advance!
Caleb from Alabama

Clemsonfor
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Re: Too much fuel to carburetor

Postby Clemsonfor » Thu Oct 29, 2020 8:18 pm

Did you set the float height correctly? Only things that will make it over flow fuel is trash stuck in the needle and seat, float being stuck or the float height set incorrectly.

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Re: Too much fuel to carburetor

Postby Crimson Tim » Thu Oct 29, 2020 8:29 pm

Or having a float that leaks so gas gets inside it.
If you take the float out, put it in almost boiling water. Do bubbles come out? Or if you shake the float, can you hear/feel fluid inside?

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Glen
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Re: Too much fuel to carburetor

Postby Glen » Thu Oct 29, 2020 11:55 pm

Hi,
Check the needle and seat for dirt in them.
The needle and seat can be wornout from use, and not seal anymore.
Usually that makes a dripping on the ground when the engine is off.

The float height is important, it should be measured and set exactly.

Bob McCarty changed the measurements in the Cub service manual to use a dial caliper, it is easier.
The float height is 1.4",
the float drop is 1.6"

If the float is upside down it doesn't work right.
The tab on the float for the float drop faces up.

Below is a page from the Cub service manual, showing the IH carburetor in the upper 2 pics.

http://www.farmallcub.info/manuals/gss- ... 002-09.jpg

To set the float height, you have to take the top half off the carb, turn it upside down, like the pic of the Zenith carb, at the lower right of the page, and measure.

To measure the float drop, turn the upper half right side up, and let the float hang down, and measure.

The gasket between the halves has to be off when measuring, for the IH carb.

Below is a listing for a new needle and seat at TM Tractor. They have carb gaskets too.

http://www.tmtractor.com/new/fl/5183fp.htm

Below is a pic from TM Tractor of the IH carb float. The tab has to face up. :)
Attachments
Cub float.jpg
Cub float.jpg (13.96 KiB) Viewed 824 times

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Re: Too much fuel to carburetor

Postby Clemsonfor » Fri Oct 30, 2020 7:21 am

Crimson Tim wrote:Or having a float that leaks so gas gets inside it.
If you take the float out, put it in almost boiling water. Do bubbles come out? Or if you shake the float, can you hear/feel fluid inside?

Yep I forgot about a sunk float.

calebpalmer86
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Re: Too much fuel to carburetor

Postby calebpalmer86 » Sat Oct 31, 2020 10:48 am

Thanks for the replies. When I took the carb apart last time I could not hear or feel fuel inside, so I do not think that the float is leaking. Is this conclusive enough or should I still put it in some hot water to be 100%?
I have also thoroughly cleaned the carb twice, so I do not think that there is any trash inside affecting the needle or seat. I wasn't aware the the float height could/needed to be adjusted, so maybe this is my problem. Is there any way to check to see if the needle and seat are bad? There is a chance that they have never been replaced and this tractor was in heavy use for many years.
I will take it apart again and ensure that it isn't upside down, and also measure the float drop.

Thanks!
Caleb

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Re: Too much fuel to carburetor

Postby Waif » Sat Oct 31, 2020 11:21 am

Be sure your carb still has the idle tube standing vertical inside the top of it.
They get broke sometimes during removal of the housings top.

Checking float drop will eliminate the question of it's involvement. More so if it is out of spec. and allowing flooding!

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Re: Too much fuel to carburetor

Postby Clemsonfor » Sat Oct 31, 2020 3:21 pm

Needle and seat are a wear item. Personally if I was going into one in which I questioned if it had been replaced in the last few decades and it had heavy use I would buy them an install them. If the money they cost is an issue for you and you don't mind pulling it off again if you measure float drop and adjustment just make sure it's clean and there is not a groove worn into the needle and put it back together. I suspect your float adjustment is your issue if you think the needle looks fine.

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Don McCombs
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Re: Too much fuel to carburetor

Postby Don McCombs » Sat Oct 31, 2020 3:40 pm

Just as a point of reference...
I have been working on IH Cub carburetors for a few years now. In that time, I have never seen a worn float needle. The original needles are made of stainless steel and the seats are made of brass. In all likelihood, the problem lies with an improperly adjusted float, a leaking float, debris in the needle and seat or leaking discharge nozzle threads. Try the hot water method on the float. It does not need to be boiling.
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Re: Too much fuel to carburetor

Postby Gary Dotson » Sun Nov 01, 2020 8:50 am

One more thought, to add to the list. Has the side of your carb. float chamber been hammered on? Are there marks from someone trying to dislodge a hanging float? We've seen many cases where the side of the float bowl had been hammered enough that the float no longer cleared the side wall. You also want to make sure the float is traveling in the center of the bowl. A slightly bent float arm can cause clearance issues. The float travels very close to the chamber walls.

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Re: Too much fuel to carburetor

Postby Stanton » Sun Nov 01, 2020 9:33 am

Just want to remind you (if you don’t already know) about the numerous threads in the How To Forum dealing with fuel: http://farmallcub.com/phpBB2/viewforum.php?f=139

I have worked on these carbs for many years now and agree with Don, the needles and seats rarely get worn out. Check float height and floatability.
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Re: Too much fuel to carburetor

Postby xrcr » Mon Nov 02, 2020 9:33 am

These measurements the same for a Zenith?

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Don McCombs
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Re: Too much fuel to carburetor

Postby Don McCombs » Mon Nov 02, 2020 10:11 am

Zenith Float Settings.jpg

If you mean the float setting dimensions, no. For the Zenith, the float height is 1 5/32 and the fuel level is 15/32.
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Re: Too much fuel to carburetor

Postby Glen » Mon Nov 02, 2020 6:14 pm

Hi,
The float height for the Zenith carburetor is shown on the page from the Cub service manual that I posted the link for above.
It is the lower right pic on the page. :)

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Re: Too much fuel to carburetor

Postby Clemsonfor » Mon Nov 02, 2020 6:38 pm

Ok, these guys know these carbs way better than anyone. What I said about just replacing a needle and seat was my experience with all other carbs I have encountered. If these after decades don't wear out then you can leave it. Like I said I do agree the float is most likely the issue from some standpoint.


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