Carb issue

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bull
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Carb issue

Postby bull » Sun May 07, 2023 10:42 am

Have a 1955 cub with a carb issue. New battery, spark plugs, plug wires, coil and points and condensor.

Bought a new carb and could not for the life of me get it to stop leaking.

Bought another off ebay (new).

Tractor starts fine, but stalls when I accelerate (or try to).

Have adjusted the air screw and almost no difference, no matter how much I go in or out (started at 1 1/2 turns out).

It idles fine.

Read the carb posts on here and can't seem to find this issue (with a brand new carb).

Any help greatly appreciated.

Eugene
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Re: Carb issue

Postby Eugene » Sun May 07, 2023 11:08 am

bull wrote:Tractor starts fine, but stalls when I accelerate (or try to).
Start with ignition timing. Make sure the spark plug wires are on the correct plugs and the ignition timing is spot on. Spark should be bright blue.

Edit. Chinese knock off carburetor?

Another edit. Do you still have the original IH carburetor?
I have an excuse. CRS.

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Don McCombs
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Re: Carb issue

Postby Don McCombs » Sun May 07, 2023 2:00 pm

CHINESE REPRO CARBURETORS FROM EBAY.pdf
(209.2 KiB) Downloaded 183 times
Don McCombs
MD, Deep Creek Lake

Image
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.
A. K. Trenfor

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Glen
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Re: Carb issue

Postby Glen » Sun May 07, 2023 6:10 pm

Hi,
You didn't say if the new carburetor is an imported one that looks like an IH carb.
People have wrote on here before about having the same problems with a new carb that you wrote.
The float level being too high can make the carburetor drip on the ground when the Cub is sitting.
You turn the top half of the carb upside down to set the float level.
The float drop should be set too, if the new carb has a stop for the float drop.
People on here like to rebuild the original IH carbs also. :)

bull
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Re: Carb issue

Postby bull » Sun May 07, 2023 9:13 pm

Yes. It is a chinese knock off.

Is there no way to adjust these things?

Is the rebuilt IH carb better than the new chinese carb?

It starts and idles fine, but it does not have a bright blue spark, more of an orange or yellow.

Why does the air/fuel screw not do anything?

Thanks much for the replies. I'm really scratching my head.

bull
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Re: Carb issue

Postby bull » Sun May 07, 2023 9:14 pm

One more update. The new carb (2nd one that I bought) does not leak.

Thanks again.

bull
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Re: Carb issue

Postby bull » Sun May 07, 2023 9:19 pm

Another update.

Just saw the PDF from Mr. McCombs. This looks like it might be something that could be affecting mine.

Going to try that (4th time I've removed the carb on this tractor).

Thanks again.

bull
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Re: Carb issue

Postby bull » Sun May 07, 2023 9:21 pm

One more quick question.

Is this a well known issue that the new carbs on ebay are defective?

TIA

Bob McCarty
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Re: Carb issue

Postby Bob McCarty » Sun May 07, 2023 9:28 pm

It seems that the Chinese carbs may be assembled at different plants. Some run fine when installed and others, like yours, don't. They can be adjusted and modified as Don's post shows. The air adjustment screw is to give a smooth transition from low throttle to high throttle. If you have a weak spark, you may have a coil or other electrical system problem (plugs, plug wires, etc.).
"We don't need to think more,
we need to think differently."
-Albert Einstein

Eugene
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Re: Carb issue

Postby Eugene » Mon May 08, 2023 6:53 am

bull wrote:Is the rebuilt IH carb better than the new chinese carb?
Opinion. Yes.
I have an excuse. CRS.

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Glen
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Re: Carb issue

Postby Glen » Mon May 08, 2023 5:10 pm

They have said on here the spark should be blue or white, and jump about a 1/4" gap, from the end of a spark plug wire, to a bare place on the block, turning the engine with the starter.
A yellow spark is weak, and the engine may not run, or run right.

If you have recently replaced the ignition points, condenser, and coil, and it has a yellow spark, doing the spark test I wrote above, something is not right, you may have gotten a defective part.
People on here have said they got defective new condensers.
TM Tractor at the bottom of the page has new ignition parts. :)


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