Farmall Super A, AV, 1939 - 1954
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Tue Dec 11, 2012 9:09 am
I replaced the original Carter carburetor on my 1951 Super A with an apprropriate new Zenith carb last fall. Performance was awesome...until recently. The new Zenith has a plastic/rubber tipped float valve. I noticed that fuel slowly weeps/seeps from the fuel bowl drain when the engine is off and when the tank shut off is open. When running, some choke is needed to keep running smooth and to optimize power. The new carb was removed, cleaned and the float checked and set to 1-5/32 inches (Zenith spec)...only a very minor adjustment needed. The unit's governor is fine and the ignition system, valves and timing are spec. Can some definitively tell me what's needed to restore performance?
Tue Dec 11, 2012 9:39 am
Have you checked your fuel tank and fuel strainer for dirt and debris? IF the rest of the fuel system is clean, your problems may be the result of using ethanol enhanced fuel with the rubber tipped float needle. I would contact Zenith to determine if their rubber compound is suitable for use with ethanol. While on the phone with them, I would see if an all-metal needle is available.
BTW, which model Zenith did you use? I may want to replace mine someday.
Last edited by Don McCombs
on Tue Dec 11, 2012 1:26 pm, edited 1 time in total.
Tue Dec 11, 2012 11:12 am
The need for the choke could be a partially clogged high speed jet.
Wed Dec 12, 2012 8:07 am
If my memory serves me correctly, my replacement Zenith carb for my Super A was a model 161. The people at Zenith are helpful with identifying the correct model...their website is all about carbs for more modern applications/vehicles.
On the questions about a clean fuel system, I checked the fuel strainer screen and found it clean...and re-cleaned it anyway. I think I may have a fuel gumming situation in the float valve seat with the rubber-tipped plunger. I think the weeping of fuel I'm experiencing is closely related to the performance problem. I'm left to "try this and try that" to find the problem and remedy it unless one of the forum members can direct me.
Wed Dec 12, 2012 9:23 am
How about the interior condition of the fuel tank? How old is the fuel in the tank? If you suspect varnish deposits may be the culprit, I would drain the tank (if the fuel is older than 90 days) and try some Seafoam in the new fuel according to the label directions.
Wed Dec 12, 2012 11:34 am
Ironlegs wrote:I think I may have a fuel gumming situation in the float valve seat with the rubber-tipped plunger.
When shutting down for the day, shut off the fuel at the tank and let engine die of fuel starvation. This will let the carburetor float drop and open the needle valve.
Don McCombs wrote:I would drain the tank (if the fuel is older than 90 days) and try some Seafoam in the new fuel according to the label directions.
Works some times and well worth a try. Drain the entire fuel system including the carburetor bowl. Install a small container of fuel system cleaner to fuel tank. Put two gallons of fresh gasoline in gas tank. Open fuel shut off. Let set for 5 or 10 minutes. Start engine.
Thu Dec 13, 2012 11:36 am
The fuel tank is in fine shape...no corrosion. I screen all fuel at the time of each fill. I shut off the fuel strainer cock after each use of the machine. I guess my next move is to remove the carb and open it up (again) to search for debris or gum. The fuel in this machine never gets older than about a month. I use about 125 gallons per year in this machine.
Tue Dec 18, 2012 10:25 am
Fellows, I have a verdict on my problem with having to choke the carburetor, even with a warm engine, and a weeping carb fuel bowl after stopping the ignition (fuel cock on). I found a piece of the paper/cardboard orifice gasket for the carb's main jet stuck immediately down-stream of the fuel bowl's outlet to the main jet. The carburetor model is Zenith (161, I believe) and was purchased new about 18 months ago. After a full carb disassembly, cleaning and removal of the card board piece, the tractor runs great (again). In place of the damaged washer, I used Permatex and an o-ring...there was no way I was going to take a chance on another paper/cardboard washer. Case solved.
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