Zenith carbs

Charlie M · Jun 23, 2018

I've narrowed down the problem with my 100 that only runs with almost full choke - its a carb problem. I swapped it with one off my A and now the 100 runs good but the A needs almost full choke. The carbs are
both Zenith but have different numbers on them. Taken apart they look almost identical. I see there are several numbers available for Zenith carbs on those tractors so I'm wondering what is different and will
any number work.

gene bender · Jun 23, 2018

You still have some dirt someplace and is the gasket good. I use a small mag lite to look in the passages to make sure they are clean. Customer just brought one the other day with same symptions cleand the passages again and new gasket runs fine now.

mattofvinings · Jun 24, 2018

I go to the "paint can" of carb cleaner for a 1 day soak, with halves separated and gasket removed. Clean up basic gunk in bowl-cavities. Dry the exterior to be able to handle without dropping. Remove anything that's a square or hex head plug. Including the main jet and sometimes an orifice is at the end of a special hex bolt. Now rod-out the holes with the wire, carefully, torch tip cleaner or piece of cu wire. Might need a few drops of the can-solvent if dirt is found. Visualize the flow to all passages and try to hit them all as best as you can. Idle jet can be the hardest. Then blow out each passage with compressed air. Get the needle moving freely. New gaskets and onto the tractor for a test.

David G · Jun 24, 2018

Did you have that carb apart?

Could be plugged passages or missing venturi.

Charlie M · Jun 24, 2018

I've had it apart a bunch of times. Cleaned with solvent, used welding tip wires to get into all the passages I could find. New kit in it. Did all things mentioned here a couple of times, no change. Only thing I can think of there is a blocked passage I don't see. I'm ready to try something different.

mattofvinings · Jun 24, 2018

The dip is a different formulation than your typical brake clean. It took all of the paint off the exterior of the carb without me scrubbing or anything. Its low effort other than acquiring the can. But any auto parts store should have it.

It got stuff out that I couldn't get with the initial brake clean and lacquer thinner. Maybe its the time in the bath that's different...dunno...but it seems like a pretty exotic formulation when reading the can.

With 90% choke needed to run, it would seem like something is wrong with the main jet or the way it compensates for atmospheric pressure, there's some kind of a little air passage as I recall.

560Dennis · Jun 24, 2018

I've had issues with 10386C carburetor for farmall c .
The idle circuit has a very small hole in it down by the main jet. You need a .04 inch drill ,which you use your fingers to twist out material clog the vent.

I also had loose intake manifold nuts that leak .
You need to check the throtle shaft for wear , I rebush the carb housing for minimal Clearence .
I use a vacuum gage to test ,tractor engine normal engine should be 18 to 22 inches of vacuum. I remove the pile plug from the intake to insert a 1/8 hose barb fitttting to hose to gage . I would predict you will start out at 14 inches of hug from what your saying .
I would record T your reading before you make any changes that way whatever you do you know if it helped or made worst.
I have crusty clogged material in gas tank that would not allow gas o flow. Took a 3/16 drill and hand drill out the white crusty stuff for better gas flow .
Ggood luck

old · Jun 24, 2018

I've run into problem like that and have boiled carbs out on the stove. Put them in a water bath and boiled them for a few minutes. Pull them out let them cool and blow them out and the use carb cleaner spray and the torch tip cleaner tool

Zenith carbs

Charlie M

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gene bender

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mattofvinings

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David G

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Charlie M

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mattofvinings

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560Dennis

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old

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