Farmall Cub

Hi guys, looking for some info on Zenith carb. bought almost new on E-bay for 40.00. I think it is running a little rich from mid-range to full rpm. I got the numbers and think it's from a later cub or lowboy. Carb # on tag, 4 02 -13794E -75123C 93 . My ? is if the main jet is too large,where can i get a replacementof the correct size?. It runs great but seems to sputter a little form midrange on up to wot wich it didn't do with the carb off my 49, it was smooth as could be at all speeds. Thanks in advance for any and all info. WLM Cub

Thinking, partial blockage in carburetor high idle circuit or float adjustment. Could also be a fuel flow problem, if the problem shows up a minute or two after engine throttled up.

E-bay carburetor.

Before I started swapping parts, I'd clean the carburetor.

It should run fine on your cub without changing anything clean the carb as Don said
Boss

Hi Eugene, I did all that and more before I put it on, Sprayed everything and cleaned all jets with carb cleaner and compressed air although it looked Brand new inside and out, then checked the float level. Good to go. Starts great and runs smooth up to half throtle then it starts to go rich form there on up to full. The needle does not leak down as I found by accident and left the shutoff open all night,no leak down at all. Thanks again for all you folks do on the fourum. WLM Cub

Thanks Don, but did that And thanks for the reply. WLM Cub.

Hi Boss, Thank you for the reply. I thought I had read in one of your posts sometine last year that the later carbs had larger main jets in them with the larger air intake hose and to change the jets to a smaller size. Maybe it was on the other forum. Anyway Thank you again for all you folks do and keep up the good work, WLM Cub

I don't think the main jet size is the problem because the main jet feeds both the low and high idle circuits in the carburetor.

If you want to you can remove the main jet. There should be a number stamped on it indicating the orifice diameter. Try carburetor shops or small engine shops to obtain a jet with a smaller orifice. Wisconsin engine parts books list about 20 or more main jet sizes for one model carburetor.

Have you check the ignition system?

Hi Eugene, just been tuned up 2 months ago and ran great until I changed the carb. I put the old one back on the 49 and the new one on this one wich is a 52. Like Boss said I'll just run it for now and keep an eye on the plugs. She purrs like a kitten at Idle and has good power at wot. Thank you again,WLM Cub

How do you know it is running rich?

Bad plugs, wires, timing, lean running, carb to manifold gasket or warp causing an air leak, severely worn throttle shaft, broken spark advance will also give the same symptoms.

The idle circuit function is basically unrelated to the size of the main jet. The main jet limits the fuel above idle speed. Regulation of fuel above idle is by the discharge nozzle and the well or air bleed jet. That jet is important and if plugged then the engine will run rich above idle speed. The other regulation of the mixture is by those little holes on the side of the discharge nozzle. Make sure all are open AND run a thick wire down the center of the nozzle to make sure the center is open to full size.

An air leak through the bowl gasket into the bowl will also cause an engine to run rich.

I assume this is a model 68 carb in which case just about any of them should work on a cub. The size of the main jet is unlikely to be the problem.

Landreo wrote: air bleed jet. That jet is important and if plugged then the engine will run rich above idle speed.

That would be a yup. Big yup.

Thanks again guys, I guess I'll try to find out what the carb came off. Does anyone reconize the numbers I first posted. Landero, Where do you find the model # 68 on the carb? Is that a IH 3 at the bottom of the tag? 21523 C93-BKMV, Thanks again all and will check back on here tomorrow . WLM Cub

does yours have 4 or 5 screws holding it together

Hi Boss, it has 5 screws unlike the one in Eugene's website picture wich shows the carb # without the E at the end. {13794 E] Also the choke rod attaches ti the inside as does the throtle. Thanl you and Eugene for your thme and patience. WLM Cub