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1947 cub carb. problems

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DLM
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1947 cub carb. problems

Postby DLM » Wed Nov 23, 2016 1:32 am

I have two 47 cubs one runs real good but the other is way over fueled i took both carb. apart to compare, the top half of each are the same floats are set right , but the bottom are different the over fueled one has a passage 1/8" wide and deep next to the air bleed hole also it has the large .100 nozzle,and a .035 main jet but the good running cub doesn't have the 1/8" grove and it has the .060 nozzle . Also has a .030 main jet.

I know Stieners list jets and nozzle for large bore and small bore carb. What is the difference between a small and large bore is it a larger venturi my thought is some one put a small bore top half on a large bore bottom half. The gasket is the same part # for all the IH carbs. Hope some one has a answer Thanks Don

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Timber cub
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Re: 1947 cub carb. problems

Postby Timber cub » Sat Nov 26, 2016 5:18 am

That sounds like a good possibility. Good luck with it.

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Don McCombs
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Tractors Owned: "1950 Something" Farmall Cub
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1948 Farmall Super A
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Location: MD, Deep Creek Lake

Re: 1947 cub carb. problems

Postby Don McCombs » Sat Nov 26, 2016 8:13 am

Air bleed, discharge nozzle and main metering jet are matched sets. Venturis are all the same. Do you know any of the history for the carb that's giving you problems? Is this a new problem, or something that's been happening as long as you've owned the tractor? What do you mean by "overfueled"?
Don McCombs
MD, Deep Creek Lake

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Bob McCarty
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Re: 1947 cub carb. problems

Postby Bob McCarty » Sat Nov 26, 2016 9:31 am

Can you read the part #'s on the carbs? It's on the flat area of the carb top adjacent to the gas inlet. I'm wondering if you have an IH carb that was modified to run on a numbered LoBoy.

Bob
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we need to think differently."
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DLM
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Joined: Wed Nov 23, 2016 12:38 am
Zip Code: 81001

Re: 1947 cub carb. problems

Postby DLM » Sat Nov 26, 2016 12:24 pm

The # on top of carb.are 251234 R 91 that is the bad carb. the good one is 251234 you can't reed the rest of the # the top half of these carb. are the same it is the bottom half that are different. I am working on this tractor for some one else. He has been running this cub with over rich fuel problem ever sense he bought it he is not very savvy on how things should run. He has two cubs so i had him bring me the carb.off of it and i try ed it and it works good on the cub i am working on so i took that carb.apart to compare with the bad one that is when i found that the bottoms were different so i modified the bad bottom to match the good one and now both work the same.What is the difference between a small bore and a large bore carb. when you look at the parts book they list a nozzle of .060 for small bore and .100 nozzle for large bore main jet .030 small bore & .035 large bore. With my modified bottom half it works ok now. Don

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Don McCombs
Team Cub Mentor
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Posts: 17446
Joined: Mon Feb 03, 2003 6:45 am
Zip Code: 21550
Tractors Owned: "1950 Something" Farmall Cub
1957 Farmall Cub w/FH
1977 International Cub w/FH
1978 International Cub
1948 Farmall Super A
Circle of Safety: Y
Location: MD, Deep Creek Lake

Re: 1947 cub carb. problems

Postby Don McCombs » Sat Nov 26, 2016 12:55 pm

Glad you got it working properly. What, exactly, did you modify?
Don McCombs
MD, Deep Creek Lake

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Proud Member of Maryland Chapter 39

The best teachers are those who show you where to look, but don't tell you what to see.
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DLM
5+ Years
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Posts: 3
Joined: Wed Nov 23, 2016 12:38 am
Zip Code: 81001

Re: 1947 cub carb. problems

Postby DLM » Sat Nov 26, 2016 8:20 pm

I plugged up the 1/8" square groove and milled the air passage on over to the other air passage and that passage had a .045 hole in it
and the good carb. had a .035 so i put a .010 wire in the bigger passage also tryed the .060 nozzle and with the modification it runs as good as it did with the good carb. i tryed to make the bottom of both carbs. the same and i seem to work. Don


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