Cub Carburator Adjustment

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farmergiffIV
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Cub Carburator Adjustment

Postby farmergiffIV » Wed Jul 05, 2017 1:34 pm

Hi there,

So I have been trying to get my cub to start- I need to make sure the carb is set as it should. I just pulled it out of the box its a new original style TM carb.

I have questions that my carburator-to-governor shaft or something with the lever rod assembly is also improperly set up and I need to make sure we are set at 1/3 throttle so I can start up.

What's 1/3 throttle supposed to look like on the throttle butterfly or the throttle lever and shaft assembly of the carb? I'd like to see if I can get the tractor idling without the carburetor-governor shaft assembled.

Right now I turned the idle adjustment screw all the way in and then back out 1 full rotation, any tips on these settings? Thanks

Also, so curious what the original choke throttle on the cub looks like, I think I need to get one as I can't run my electric start w/ out it.
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Glen
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Re: Cub Carburator Adjustment

Postby Glen » Wed Jul 05, 2017 11:36 pm

Hi,
Be careful tightening the gas line connection, or the mounting studs on the IH carburetor, it is soft metal, the threads strip out tightening things too much.
I have found that the idle mixture screw usually needs to be set about 1 1/2 turn open, on the IH carb. The owner's manual tells how to set it. It says warm up the engine before making the setting.

I guess you are saying you don't have the choke lever on the carb, or the choke rod.
The choke rod has a loop on the top end that matches the starter rod loop. The choke rod goes on the left side of the dash.
Here is a new choke rod at TM Tractor, and a new choke lever for the carb.


http://www.tmtractor.com/new/fl/934fp.htm

http://www.tmtractor.com/new/fl/522fp.htm

Here is a pic of from TM Tractor of how the lever for the choke rod goes on the carb, it usually has to be in this position.
Below are pics of the choke rod in position. :)
Attachments
Cub carb.jpg
Cub 3.jpg
Cub.jpg

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farmergiffIV
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Re: Cub Carburator Adjustment

Postby farmergiffIV » Sun Sep 17, 2017 9:45 pm

Thanks for the helpful information Glen. I'll be getting a replacement choke rod soon. Luckily, I traded a couple of my piglets to a professional mechanic for his trade in some tractor help and he's helped me demystify the carb a little since my original post.
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Re: Cub Carburator Adjustment

Postby outdoors4evr » Mon Sep 18, 2017 9:10 am

Most adjustable needle valves will be "close" if you turn them in all the way and back them out 1.5 turns.
Finger tight closed is plenty. Don't overtighten it.
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Re: Cub Carburator Adjustment

Postby Matt Kirsch » Mon Sep 18, 2017 12:36 pm

If the governor is working properly you "time" the governor to the carburetor by disconnecting the throttle rod on the left side from the governor up front (yoke with a pin through it). Push the throttle lever all the way ahead, which should cause the governor to move ahead where you just disconnected it. Now adjust the length of that throttle rod by turning the yoke in or out on the threads until the pin will just slide through the yoke and governor arm easily, while you hold the throttle on the carburetor wide open.

Generally speaking it does not need much adjustment, so if you find yourself turning it in or out by more than 1 or 2 revolutions, you may be doing it wrong.

Once this adjustment is done the throttle lever should properly control engine speed.

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Re: Cub Carburator Adjustment

Postby Glen » Mon Sep 18, 2017 4:36 pm

Hi,

Matt, here is a page from the Cub service manual, GSS-1411 telling how to adjust the throttle rod, you were talking about. It says open the throttle about half way, not fully. Notice the subject is at 1 on the right side of the page, and then read paragraph A below that.

http://www.farmallcub.info/manuals/gss- ... 002-18.jpg

Then there are 2 more paragraphs on this page, if anyone is wanting the whole procedure. :)

http://www.farmallcub.info/manuals/gss- ... 002-19.jpg

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Re: Cub Carburator Adjustment

Postby farmergiffIV » Sat Jan 20, 2018 1:50 am

I find myself back to the carburator now... My "new" '53 is hard to start up. I'd like to get it to start up great and just purr. I haven't looked at the plugs or wires yet but I will double check Coil spark tomorrow and then follow to the spark plugs. But I wonder if its the carburator. I usually flood it if I don't get it just right and then I just myself trying to start with starter fluid or pulling the drain plug on the bottom of the carb to let it air out... Once the engine is running, she runs good and doesn't overheat. But even just after running for some time seems hard to start again so I took the carburator off and inspecting the float action it appears to work as it should... Except when on the tractor the carburator seems to flood if the tractor isn't running, (so I always turn my in-line fuel valve off) maybe this makes sense since the carburator float is supposed to keep fuel in the bowl.

-I'll check the idle spring tomorrow and then double check the governor is adjusted properly to the carb. Also I am so tired of those carburator attachment holes stripping out, going to jd weld the carburator mounting bolts to the carburator body on this one.
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Re: Cub Carburator Adjustment

Postby Crimson Tim » Sat Jan 20, 2018 3:07 am

Running ok, but hard to start due to flooding sounds like a needle valve issue. If the valve won’t seat, it will continue to pour gas into the carb. If the engine is already running, it will keep ahead of the flood if it’s not too bad. If the engine stops, though, it will flood and it won’t start.

It could be as simple as crud in there interfering with the valve closing. Clean the needle valve (and the jets and screens while you’re in there for good measure).

Check both the float height and float drop if you haven’t already, and then check if your float leaks. Try shaking it. If you feel/hear fluid in the float, you’ve got a leaker. If it seems ok, try a final check of submerging it in very hot water. If it gives off bubbles, it leaks.
A float that leaks becomes too heavy and so will also cause the carb to flood.

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Re: Cub Carburator Adjustment

Postby Jim Becker » Sat Jan 20, 2018 12:38 pm

Does gas eventually start to drip out of the carburetor if you turn on the gas and just let it sit there without trying to start it? If not, the needle valve isn't leaking.

This sounds like you are over choking it when you try to start it. Do an ignition tune-up then go easier on the choke.

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Re: Cub Carburator Adjustment

Postby Eugene » Sat Jan 20, 2018 12:54 pm

Jim Becker wrote:Do an ignition tune-up then go easier on the choke.
Yup. Ignition has to be spot on. Firing the spark plugs a degree or two prior to the piston reaching TDC will make the tractor hard to start.

You might want to do a complete engine tune up; compression tests, valve tappet adjustment, etc..
I have an excuse. CRS.

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farmergiffIV
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Re: Cub Carburator Adjustment

Postby farmergiffIV » Sat Jan 20, 2018 7:49 pm

Jim Becker wrote:Does gas eventually start to drip out of the carburetor if you turn on the gas and just let it sit there without trying to start it? If not, the needle valve isn't leaking.

This sounds like you are over choking it when you try to start it. Do an ignition tune-up then go easier on the choke.


Yes, it dribbles a lot... :tractor: Sounds like the needle valve might be leaking. I just inspecting it, perhaps the float is catching or the needle valve. I can



Eugene wrote:
Jim Becker wrote:Do an ignition tune-up then go easier on the choke.
Yup. Ignition has to be spot on. Firing the spark plugs a degree or two prior to the piston reaching TDC will make the tractor hard to start.

You might want to do a complete engine tune up; compression tests, valve tappet adjustment, etc..


I am going to start with electronics and make the carburator snug as a bug up to the mount. If I don't get feedback I will surely move onto the valve tappet...

8)
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farmergiffIV
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Re: Cub Carburator Adjustment

Postby farmergiffIV » Sun Jan 21, 2018 6:26 pm

Does anyone know how to tell if the main metering jet is out of alignment. I took both carbs apart and I have two different metering jet hole angles. While looking into the bowl one hole is facing 90 degrees parellel to the bottom of the carb the other is more of a 45 kinda making alignment with my eyes if I drew a line in its direction the hole would just point towards the bottom upper lid of the bowl.
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Re: Cub Carburator Adjustment

Postby Don McCombs » Sun Jan 21, 2018 6:41 pm

The alignment doesn't matter.
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farmergiffIV
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Re: Cub Carburator Adjustment

Postby farmergiffIV » Sun Jan 21, 2018 7:17 pm

Don McCombs wrote:The alignment doesn't matter.



Ok then, this is good to know. Thanks Don.

Anyone out there can tell me if its easy to remove the breaker chamber cover while the electronic ignition unit is still mounted and timed to the cub? I just want to get in there and check the points but I am too lazy to retime. The manual doesnt say this but it appears the screws on the outside might loosen the cover, one in the back facing the engine is real hard to reach...
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Re: Cub Carburator Adjustment

Postby Bill Hudson » Sun Jan 21, 2018 8:05 pm

farmergiffIV wrote: My "new" '53 is hard to start up. I'd like to get it to start up great and just purr...


Yes, I know what you mean. I've got a '42 model that is the same way. Starts cranky and creaks a lot. '42 model? Yes, me. :D :D I'm sorry, I couldn't pass up the opportunity.

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