Problem with carb cub won’t run.

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CaptainMoyer
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Zip Code: 000006

Problem with carb cub won’t run.

Postby CaptainMoyer » Thu Dec 12, 2019 10:16 am

So first of all I used to be SteveinMo but had log in problems. I have a 1958 cub that I failed to run much this summer. So of course now it will not start but only runs on starting fluid. So I pulled the carb out and let it soak in cleaner tank for 24 hours. Drained the old gas and refilled the tank. I did take the carb apart. Put it back on and it is no better. Got a rebuilt kit and redid the Cleanning. I used a needle to insure all the holes and the pick up tube (?) are open.
Still no start. Now here is the interesting part. If I let is set for a minute or so it will try to start hits once or twice and then just back to cranking. Leave it set again and then it will try once more.

You guys have always been great help. I hope you can help me again. Thanks.

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Lt.Mike
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Re: Problem with carb cub won’t run.

Postby Lt.Mike » Thu Dec 12, 2019 10:42 am

If you remove the main jet plug in the carb bowl you get fuel right? If so it still may be clogged somewhere. With the fuel line at the carb off does it flow out freely? Is it a zenith carb? If so remove the inlet elbow on the carb. There is a mesh screen hidden inside that can clog.
I also had issues with chips of rust from the tank clogging the inlet to the sediment bowl. Using a thin rod I poked inside the tank into the inlet to bust the crud up and I’d see it flow down into the bowl. That’d work until more crud clogged it again. A proper fix would have been to drain and clean the tank but I installed an inlet screen and it hasn’t been a problem since.
One you verify fuel flow check for spark, compression as maybe a valve stuck open.
Quote by Gary Pickeral I like
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Bob McCarty
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Re: Problem with carb cub won’t run.

Postby Bob McCarty » Thu Dec 12, 2019 10:43 am

It sounds like a fuel problem. Remove the drain plug on the bottom of the carb and make sure you have a good steady stream of gas for a minute. If you don't, then there is an upstream blockage. It could be the needle sticking, debris in the inlet screen or debris in the sediment bowl/screen. Even though you have cleaned it, you might want to remove the main jet again and make sure that orifice is open.
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Waif
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Re: Problem with carb cub won’t run.

Postby Waif » Thu Dec 12, 2019 12:19 pm

You could switch to carb cleaner instead of starting fluid. The starting fluid is harsh on an engine if more than a dab is used.

Not easy , but patience comes into play on a no start. It's easy to be too hard on a starter and system....(I know from being there too.)

What condition the tractor was parked and stored in comes into play. Are plugs good and gapped properly? Strange enough but that has been part of my problem more than once. One time it was only one plug that was the problem.
Are points clean? (Setting can be hard on them,corrosion from moisture is just one effect.) Proper gap?

Check your vent on your gas cap , and as mentioned your gravity fuel flow.
It could be fooling me , but the delay after setting could be fuel flow restriction related. A poor vent or flow can do that. Only way to be sure is to inspect.

When not having recent tune up specs,wear can get to a point that starting gets hard with addition change. Suspected fuel delivery in your case.
But symptoms can be tricky to diagnose when multiple causes are behind them.

It takes a healthy dialed in Cub to start in the cold.
Don't know where you are but if you are near or below freezing , folks here have had good success pre-heating the exhaust manifold area with a heat gun or hair dryer.

As ever on a no start , double check your ignition switch or kill switch if one exists for good contacts and destinations contacts.

CaptainMoyer
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Zip Code: 000006

Re: Problem with carb cub won’t run.

Postby CaptainMoyer » Fri Dec 13, 2019 4:29 pm

So i checked the fuel flow today,it seems plenty strong. The thing that gets me is that it starts right up but only runs for a very short time. Could the float be out of adjustment. After a short time it will start right back up again but then dies as if starving for fuel. If someone could give me the information on adjusting the float I will try that next I think.

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Don McCombs
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Re: Problem with carb cub won’t run.

Postby Don McCombs » Fri Dec 13, 2019 6:43 pm

What do you mean by "a very short time"?

Image
Notice that the dimensions are measured without the gasket in place.
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CaptainMoyer
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Re: Problem with carb cub won’t run.

Postby CaptainMoyer » Sat Dec 14, 2019 2:06 pm

I would say 15 to 20 seconds. It sounds at that point to be starving for fuel. So I see by the pictures what I am striving to achieve are there any instructions on how this is accomplished

Do mean to be a pain, I do appreciate the help.

Bob McCarty
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Re: Problem with carb cub won’t run.

Postby Bob McCarty » Sat Dec 14, 2019 2:47 pm

Carefully separate the halves of the carb and remove the gasket. With the needle closed (carb upside down) measure from the gasket surface to the top of the float. I use 1.4" as the float height measurement. To adjust it, place a needle nose next to the float on the hinge arm and gently bend the float up or down to the correct height. Then, turn the carb upside down so the float drops. The float drop should be 1.6" from the gasket surface to the "bottom" of the float. The adjustment there is to remove the hinge pin, and then bend the little tab in or out to correct the drop. It usually takes me 3-4 times to get it just right. After the drop is adjusted, turn the carb over again and recheck the float height. Also make sure that the float is centered so that it doesn't rub on the sides of the bowl. While it is apart, turn the top upside down several times to make sure the needle is dropping. Viton needles will sometimes stick sporatically.

Edit: Where I say "gasket surface" I mean the metal edge that the gasket would rest against, both measurements are made with the gasket off.
"We don't need to think more,
we need to think differently."
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CaptainMoyer
Posts: 8
Joined: Thu Dec 12, 2019 9:14 am
Zip Code: 000006

Re: Problem with carb cub won’t run.

Postby CaptainMoyer » Sun Dec 15, 2019 9:48 am

Bob, thanks so much for the help. It is 22 degrees here at my place today with so coming in. I gues this will have to wait for a few days. Anyway thanks to all of you on here for all the help.


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