Model A Zenith Carburetor

Badpuppy said:
Not sure what's the point of those. If they ever clog, you still have to pull the valve.

Easy to check for leaky valve - just empty the sediment bowl & see if it fills up again.
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They stick up about an inch or so in the tank. Would take a lot of junk in the tank to block this filter.
 
Tom Wesenberg said:
I lapped my original leaking tank valve more than 20 years ago, and it still holds perfectly.
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Tom, please tell this guy that does not know much about this subject, what you mean by "lapping". Sorry, I think you may have done this before but the old mind forgot.
 
I don't remember if I spun it some in my lathe and used a little crocus cloth to help polish it, but I do remember using toothpaste and turning it by hand. I think I may have used fine valve grinding compound, then toothpaste. I then gave it a thin coat of grease and installed a new shaft seal kit from one of the parts houses, Bert's, Bratton's, and Snyder's.


Before doing this the handle was hard to turn, and ever since the lapping and greasing, it is very easy to turn.
 
MikeK said:
Hairline casting fracture radiating up from the center through bolt bore. May not be visible at all. It is also possible that the casting itself is porous (a casting defect).


You could drive yourself nuts trying to find it or seal it but Zenith bottoms are plentiful. Replace it.
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I have repaired a few of the newer manufactured Zenith carburetors and noticed that the inside of the housing has a dull black coating. Is that a process by the manufacturer to help eliminate housing porosity? I know that through capillary action, gasoline, with it's very low viscosity can/will find the smallest pinhole in a casting.
 
SeaSlugs said:
generally why they leak is the brass is scored from microparticles of rust dirt rocks what have you. you can in theory lap them back together but even then gas and its capillary ways will find a path. Its relatively free to try to lap them back together but dont be surprised when it doesnt work well. When you install a new one or reinstall the old make sure you have a pencil filter in the top.
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Been there, try as I did, the time spent lapping and trying to seat the old valve was an education in futility. Hours were spent and in the end a new valve was installed and problem solved. I've been doing this sort of repair work for over half a century but I had to try. For the price of a valve, if the old one needs more than cleaning I would replace it. The voice of experience says that lapping two equally scored surfaces together will not end up with a smooth leak free surface. Not only will they leak to the carburetor but the stem can also leak inside the passenger compartment.
 
redmodelt said:
I pulled a Zenith apart and filled the bowl up to just below coming out the jet with mineral spirits. While the fluid did creep up the sides to the inside top edge, after 2 plus hours it had not gone over the top and down the sides. I would have tried gas but didn't have any handy.
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Follow up on test; After almost 3 days, the mineral spirits are pretty much at the same level in the bowl except for some evaporation and only a couple of damp spots on the face where it is machined for the top.
 
Here is a quick fix for a leaky gas shut off value. I put one of these things on my huckster years ago. The short term advantage is that you do not have to drain your gas tank. But the long term disadvantage is that you have to turn on two dxx values every time you start your rig. Most vendors carry these things if you are interested. This is on my 29. Don't know if these work on 30/31's.
 

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I use mineral spirits when bench checking float levels and float valves. Works well and I think safer than gasoline albeit still flammable. It has always worked well for me.
 
I have the shut off valve that is shown in post 27 and since I installed it, I have not moved the original shut off valve at all. I just leave it open and use the new one which is a 1/4 turn ball valve and much better than the original. It will not leak and so when I park our A at night, in the garage, I shut off the gas and let the engine run for a couple of minutes and then shut it off and have no gas smell or leak at all. If you happen to have a carburetor that leaks through the casting and you don't want to purchase another one right now, then when you turn off the gas with the new valve, just run the engine until it empties the carburetor completely and stops running. When you next drive your A, turn on the new gas valve and let gas run down into the carburetor before you crank it over. Ernie
 
So far only one person has posted a link that talks about float level. If the float level is correct and the float valve at the carb is working it will or should not matter if the shut off valve is left open or closed. Unless the float valve is not sealing to the upper casting or there is a crack or porous casting. No word from original poster.



Lots of good information given here, but it has been 6 day and not a word from the original poster. I for one am wondering if the question is for real. I see a number of postings in the "Questions and Suggestions" section by one time posters that A; on the surface look real but generally are just a little off and B; when told to ask in the correct forum never do. I hope this is not the case and any and all information that has been give help him or others.
 
I have read all the posts and as a result I went back to check the manual shutoff valve. I removed the gas line between the settling bowl and carburetor and hung a can to catch any leaks. The first overnight I had about a tablespoon of gas in the can and the second night I had about 3/4 of a teaspoon in the can. I decided to order an electric shut off valve from Snyders to try this. I will install it when I receive it let you know. The present manual shutoff valve is less that 1 year old.
 
Yes, I have the screen in the tank valve, the screen in the carburetor and a cartridge filter in the line after the settling bowl. I want to thank everyone for their input on this problem and I have learned a few new things to check from your input.
 
I am new to this forum so I am sorry that I did not reply sooner. I guess it did not occur to me to reply sooner and I will try to respond sooner in the future.
 
redmodelt said:
So far only one person has posted a link that talks about float level. If the float level is correct and the float valve at the carb is working it will or should not matter if the shut off valve is left open or closed. Unless the float valve is not sealing to the upper casting or there is a crack or porous casting. No word from original poster.



Lots of good information given here, but it has been 6 day and not a word from the original poster. I for one am wondering if the question is for real. I see a number of postings in the "Questions and Suggestions" section by one time posters that A; on the surface look real but generally are just a little off and B; when told to ask in the correct forum never do. I hope this is not the case and any and all information that has been give help him or others.
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I believe that the fuel shut off valve is/was an added precaution due to the location of the fuel tank. This was a common practice on most machinery that had a gravity feed fuel system. My friend who is 91 has owned his Model A for 5 years and has never closed the valve and his carburetor has never leaked a drop. The B2 carburetor on my Model A doesn't leak either, but I still shut it off. My problem is remembering sometimes to turn it on. Kind of embarrassing in a busy parking lot.
 
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