Bendix carburetor woes

Greenthumbfarms

Greenthumbfarms

Well-known member
I have a 1975 cub that has a "bendix" carburetor. Looks identical to a Zenith if you ask me...

I had put a new sediment bowl on, and had to remove the carburetor to reattach the fuel line. Ever since the cub struggles to run unless the choke is fully closed, and even still it runs pretty rough. Should I replace the gasket from the carb to the manifold? Or do I need to rebuild.my carb?

On another note the governor on this tractor has been a little "jumpy" recently...I'm still a fairly new cub owner...is this normal?

*my photos say they are too large to attach...can someone explain how to make them a smaller size to fit?*
 
I should have added that the fuel line has been leaking ever since. I tried a new line from Steiner and it leaked worse than the old so I switched back to the original
 
Did it run ok before this operation?

Four things I would check. If it runs better with choke, then the mixture is too lean. The choke reduces the air resulting in a richer mixture.
1. Fuel restriction. Maybe swapping out the sediment bowl knocked loose some rust or other crud, which lodged downstream. I would clean out the entire fuel line from tank to carb, paying special attention to the screen at the carb inlet (a zenith should have one integral to the brass elbow) and the orifice. If there is any junk in the tank, this is likely the problem. Some like to run an in-line filter in the fuel line, but it has to be one for gravity feed (no fuel pump). Also, I find a little moisture in the tank will make even the right inline filters not flow so well.

2. Air leak. Is it sucking in air between the manifold and the carb? Spray some carb cleaner or ether in this vicinity. If the engine revs, then it is. Replace the gasket and snug it down. Also, the tops of IH carbs often warp, letting the carb itself leak air.

3. Any time the carb is removed, the governor linkage should be recalibrated. This won’t change how the engine runs, but it will affect how the governor responds.

4. Take the air inlet hose off the carb and verify that the choke plate is in the correct positions relative to the choke pull. If it is loose or if you didn’t reattach the choke rod (cable, if zenith) right, the choke might be closed when you think it is open and vice versa.

I don’t recall exactly when they switched to the Zenith carbs, but I think yours would have come with one in 1975 originally.
 
While recalibrating the governor linkage, check for any slop any place. You don’t want any. Nor do you want any binding.
They keyway where the transverse linkage rock shaft behind the radiator attaches to the governor is somewhat prone to wear and “wallering”, though any of the cotter-pinned joints could, too.
 
If you have a "long strip" 75 it would have the zenith/bendex carb.

as Tim said No matter how careful you are when you remove the carb you have to reset the governor linkage. I would replace the carb manifold gasket as well.

I would also look at the cotter pins. I have had cotter pin around the carb we too long and get in the way of clean movement of the linkage.
 
I'll toy with those suggestions on it. Other than a "jumpy" governor that was slow to even off it ran like a champ before this.

Yes, 75 longatripe.

How should the governor be recalibrated?
 
It involves adjusting the length of the linkage rod between the carburetor and the governor rock shaft. The procedure is spelled out in the service manual.
 
Also, down low on the back of the carb. you'll find a brass plug. Behind that plug is the main metering jet, which may be plugged. I'd start the trouble shooting process with a fuel flow test. Remove the above mentioned plug, turn on the fuel and run fuel into a clean container for a full minute. At the end of the minute, you should still have a good unbroken stream of flow. The results of this test tell which direction you need to go.
 
Hi,
It sounds like the main jet could be plugged some, or mostly, if the engine isn't getting gas.

Below are pages from the Cub parts manual, showing the Zenith carburetor.
The main jet, number 20 in the parts pic, screws out of the carb. You need a screwdriver that fits it well, they have said on here to grind one to fit, if you don't have one.
The main jet is under the plug, number 18 in the pic.

http://www.farmallcub.info/manuals/cub_ ... 012-14.jpg

http://www.farmallcub.info/manuals/cub_ ... 012-15.jpg

The inlet fitting, number 2 in the parts pic, has a screen. Be sure the screen is clean.

You should set the float height, when you have the carburetor apart.
Below is a page from the Cub service manual, showing setting the float height. The Zenith carb is in the lower 2 pics on the page. The IH carb is in the upper 2 pics.
You have to turn the top half of the carb upside down, like in the lower right pic, to check, or set, the float height.

http://www.farmallcub.info/manuals/gss- ... 002-09.jpg

I would get the engine so it runs normally, with the choke off, before setting the governor linkage.

Below is a pic from TM Tractor, showing the plug over the main jet, at the lower rear of the carb. :)
 

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I'll work on it this week. We are reroofing our shop unexpectedly, so the cub will have to wait a week.

I'll get out my service manual and start studying...
 
Does anybody have a carburetor model number for the Zenith/Bendix carburetor so I can order a new gasket from Napa? I'm away from the shop at the moment and can't check myself
 
Geenthumbfarms":1e43jius said:
I'll see what they come up with. Realistically I just need the gasket where the carb bolts to the intake manifold
Click to expand...
If that's all you need, make one.

Gasket material from auto parts store, sharp knife and either hole punch or ball peen hammer. Probably 15 cents in material and 5 minutes time.

Edit. I would sort through my left over gaskets. More than likely I would have one on hand.
 
In that case I'll pick up a sheet of gasket material. Somehow in all my years of wrenchibg on engine's I've never made a gasket, I always just bought them
 
When purchasing gasket material, get the same thickness or thicker than the original. Otherwise, you may find the throttle butterfly may contact the manifold.
 
Hi,
The mounting gasket for the IH carburetor is thick.
Below is a listing for it at TM Tractor, they don't seem to have one for the Zenith carb, but you can look at the pic of the thickness.
Don't buy one for the IH carb, the hole is too small, I think.

http://www.tmtractor.com/new/fl/463fp.htm

I measured a new one I have for the IH carb, that is from Case IH, it is .070 thick.

I haven't seen a pic of the zenith mounting gasket, I suppose it is thick too, but I don't know.

Do you know Don, or Bob if the Zenith mounting gasket is thick.

I suppose they are thick to help keep the manifold heat away from the carb. :)
 
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