Cub dies starts right back up.

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Rusty red
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Cub dies starts right back up.

Postby Rusty red » Wed Aug 25, 2021 8:38 pm

My 53 cub dies while mowing. I can place my hand over the carb air inlet to choke it 'since for some reason the choke rod wont completely choke it' and it starts right up. Runs for a couple of minutes and dies again.
The first time it happened I pulled and cleaned the sediment bowl. it had some trash in it. When I reinstalled it fuel wouldn't hardly run into it dug around the inlet with a wire and it was getting fuel. Parked it in the shed for a week. Fired right up. Mowed for about half hour it died again. Again I could choke it with my hand starts right up and trails a little gas out of the carb. Runs for a few minutes and dies again. It has a zenith carb. It is to to hot here in swamp east Missouri to mess with it to long at a time.
Thoughts on what's happening?

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MiCarl
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Re: Cub dies starts right back up.

Postby MiCarl » Wed Aug 25, 2021 8:51 pm

The gas trailing out is normal on start, especially with choke (or a hand over the intake).

Sounds like you still have a fuel delivery problem. There is supposed to be a strainer in the carb inlet that could be the problem. Could also be at the sediment bowl or the fuel line. Also a plugged vent on the gas cap will do that.

First thing I'd try is the cap because that's the easiest. Run it until it dies and remove the cap. If you hear air rush in you've found the problem.
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Mht
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Re: Cub dies starts right back up.

Postby Mht » Wed Aug 25, 2021 8:56 pm

Cutting off and then immediately starting back up sounds like a fuel flow issue. It is a fuel restriction somewhere. I would start back at the sediment bowl since you’ve had a problem there before. If you have crud in the tank you might need to remove it and clean the tank or the problem will be reoccurring. I had one that did the same thing. I finally got tired of having to clean the inlet to the sediment bowl so I cleaned the tank out and have had no more problems. If the obstruction is not in your sediment bowl inlet then next check the inlet screen in the carb. Check main jet after that and then move to the needle and seat.

Rusty red
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Re: Cub dies starts right back up.

Postby Rusty red » Wed Aug 25, 2021 9:20 pm

When it was slow to fill the bowl I removed the fuel cap. It didnt make a difference in the flow rate to the sediment bowl.

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Re: Cub dies starts right back up.

Postby Dale Finch » Wed Aug 25, 2021 9:31 pm

If you think the choke isn't working right, it could be that the lever where the choke rod attaches to the carb is slipping on the choke shaft. This is fairly common. I believe that the carb choke shaft is knurled, and can wear smooth, allowing the lever to slip. Usually you can just line it up to the correct position, then tighten the little screw clamping it more securely onto the shaft.

It should look something like this (on the engine side of the carb, though):
c4300s.jpg
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Glen
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Re: Cub dies starts right back up.

Postby Glen » Thu Aug 26, 2021 1:00 am

Hi,
When you remove the gas strainer bowl under the gas tank to clean it, and put it on again, the air can't get out of the bowl until the needle valve opens in the carburetor.
Other people on here have said it has an air lock, so gas can't run much into the bowl.

IH started using Zenith carburetors on Cubs in mid 1975. They changed then to a cable choke, the cable connects to the side of the carb facing out.
People that put a Zenith on an older than mid 1975 Cub I guess often put the lever from the IH carb on the Zenith, like is pictured above, and use the choke rod.

Without being there I can't see if it is connected right.

Dale's pic shows the position the lever usually should be in when the choke is fully open, and the choke rod is the original length.

Below is a pic of the choke rod routing. It should be slightly above the Touch Control tubes.
If the rod is rubbing on the tubes, the engine vibration can wear the rod into the tubes over time.
If the rod is too low, increasing the bend in the rod where it is bent in the pic should raise up the rod.
You probably need to remove the rod to bend it.

The main jet may need cleaning, like was said above.
The main jet is under a cap at the bottom rear of the Zenith carb.
Below is a page from the Cub service manual showing the Zenith carb.
The cap is number 18 in the pic, and the jet is number 20.
Number 18 is called the lower plug in the description.
If you try to remove the main jet, one of the experts on here said to grind a screwdriver so it fits good in the jet, If you can't find a screwdriver that fits it, don't let the screwdriver slip in the jet.

Number 2, the elbow and strainer might need cleaning. :)

http://www.farmallcub.info/manuals/gss- ... 002-10.jpg
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SONNY
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Re: Cub dies starts right back up.

Postby SONNY » Thu Aug 26, 2021 6:57 pm

clean out the load jet. it only takes a hair to plug it enough to cause gas starving. also the long tube inside the carb will get stuff in the little side holes,---check all of that to be sure everything is open.
Dirty tank should be fixed first then go down from there cleaning everything as you go. ---- had one here that did that and never did get the tank cleaned so it would run very long, ended up mounting a big old plastic gas tank off a Dixon mower on it. -- the guy that bought the cub still runs it on that tank today.


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