Farmall Cub Forum -- Questions and answers to all of your Cub related issues.
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Tue Oct 16, 2012 3:48 am
I've had my cub for about two years now and it runs to my satisfaction for as much as I use it.
However after reading this forum for quite a while , I suspect there are a few things that I ought to check out.
I have noticed that I never have to pull out the choke (almost never) to start her even in the winter. She starts right up with the throttle only advanced about quarter open . She does smoke when first started sometimes (light smoke) and after getting warm and the throttle advanced forward the smoke lightens up quite a bit till it gets fairly clear. When I changed my plugs this summer the plugs had quite a bit of black carbon on the electrodes. I suspect that the carb. is set a little too rich. Any ideas?
Tue Oct 16, 2012 6:38 am
I agree! While it's nice that the tractor starts without the need to choke, that's an indication of running quite rich. There's not much to adjust on the Cub, you can lean the idle mixture which may help slightly and you can check the float level, which may be a little high. You can also remove the main jet and measure it with a number drill to see which jet is in it and maybe replace it with the smaller one. A lot of Cubs run richer than they should, once in a while I'll run into one that's a little lean. For my Cubs, I've made adjustable main jets so I can tune them for the best all around performance.
Tue Oct 16, 2012 7:10 am
Mr Ziffel wrote:I've had my cub for about two years now and it runs to my satisfaction
If it is running to your satisfaction I would highly suggest leaving it alone. Don't open a can of worms needlessly.
While your diagnosis is probably correct, as the previous poster stated there isn't much to adjust. Unless you spend a considerable amount of time at curb idle, the idle mixture screw is not going to cause excessive carbon.
I have 2 cubs that fire almost immediately without choke. When it gets really cold, the choke has to be feathered to keep them running once started until it warms up. I encourage people to start cranking before choking to prevent hard starting due to an over rich fuel / air mixture as well as flooding.
If you do have a mechanical issue, look for it to be at the choke rod where it attaches to the butterfly assembly. Pull the hose to the air cleaner and determine that the choke is fully open when the choke rod is pushed in. If it is partially closed with the rod pushed in, you have determined why it starts easily and tends to carbon the plugs. Adjust the choke shaft as necessary.
Tue Oct 16, 2012 8:05 am
Thanks for the input guys, I appreciate it. I'm not going to monkey with it unless it
gets bad. I really wanted some confirmation on my own thoughts of why it runs that way.
Like the man said, leave well enough alone.
Tue Oct 16, 2012 8:12 am
I just did a complete rebuild on Betty Lous carb. viewtopic.php?f=1&t=73999
Now she doesnt need the choke to start. I love it.
Tue Oct 16, 2012 11:35 am
Mr Ziffel wrote: I'm not going to monkey with it . . .
This is probably the best plan. The only thing I would consider doing is getting the proper fitting and a transparent tube to check the float height without having to take it apart. If it checks out as way too high, consider disassembling and adjusting.
Tue Oct 16, 2012 4:58 pm
Jim Becker wrote: The only thing I would consider doing is getting the proper fitting and a transparent tube
Actually, I was able to find a zerk fitting that fit the drain plug threads. Drilled out the center of the zerk, and the nipple is perfect for sliding a plastic tube onto for checking the float height.
Tue Oct 16, 2012 5:13 pm
I am guessing we are talking about fluids seeking a common level correct?
That's some good information . Thank you all.
Tue Oct 16, 2012 5:30 pm
Yep, the clear tube attached to the bowl drain then raised up above the carb as the fuel is turned on will indicate the level of the fuel inside the float bowl just like the glass tube on the 100 cup coffee urn.
But before pulling the plug and getting gas on your hands, pull that air cleaner hose to ensure the choke is not partially closed when the choke rod is pushed all the way in.
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