Zenith Overflow

J

jsilvestri

Member
Hi, my Zenith carburetor is leaking badly and I've cleaned it and replaced key gaskets.....it seems to be leaking from the engine side and when I took it off (for the 4th time) I noticed a HOLE towards the top - where I could see the tops threads of the main bolt that holds the 2 halves together, when I look into that hole. I can't recall.....is this opening normal or did some plug fall out? Seems like the fuel shouldn't be going that high anyway, but....

Any ideas, good friends?

John S
 
That hole is a vent to the atmosphere; nothing fell out.

Does it leak a big puddle or just a few drips and enough to stink up the garage? If the latter, before you turn off the engine, try running it dry after shutting off the gas valve. Sometimes thermal expansion after shutdown causes some overflow until everything cools back down.

If a big puddle, it could be the float valve--either stuck open, dirty, or sunk float.

Steve
 
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If the gasket between the upper and lower half gets damp and the carb appears to be leaking from the back side you have a bad gas line connection to the carb ; may not be seating or the farrel is bad.

Ron
 
Hi John,
Your float valve is probably leaking and then the gas fills up the bowl and when it gets to the top it over flows thru the vent hole. The float valve is controlled on and off by the brass float going up and down. Down to let more gas in, up to shut off the flow when full. Make sure the valve itself is clean. You will need to remove the float (there is a pin) and then remove the valve with a wrench an blow it out with compressd air and then reassemble. Then test.......
Good luck,
Ken
 
If the bowl was getting full enough to run out the vent hole, the gas would be running out the top of the main and cap jets before it ever got that high.

Ron
 
I found that a repo gasket was too wide at the front of the bowl and the inner overlap was catching the float preventing it from raising. I trimed the inside of the gasket and all was well. I have also seen the float catch on rough casting at front of bowl - remedy with a dremel.
 
Hey guys....thanks for the great advice! I checked a lot of the stuff out and...

I am still struggling with it....for some reason.

When I put everything back together...new float valve and all cleaned...and then turn the fuel valve on, the carb is bone dry for about 5 minutes! Then it starts leaking bigtime.....puddles...so much fuel that it's hard to tell where it's coming from (like a leaky roof...where's the hole?)....I did the "level test" and the fuel level is about 5/8" below the main gasket....so that seems OK....but, it continues to leak.....the fuel line could be the culprit, Ron, how is that?

If anyone has any other ideas, I'm all ears, scratch that, eyes.

John Silvestri
 
If you test a float in boiling water you will know if it is good or not. It is possible to have them "seem" fine, and still have a leak. A leaky float is one possibility, but of course, not the only one. Good luck.
 
John,

It shouldn't take but a few seconds to fill the carb bowl, not 5 minutes. I have found some of the replacment float valves to be too long when seated and it will restrict the gas flow.

Another trick I have done for many years is putting a thin film of Permatex Aviation Gasket Cement on both sides of all jet gaskets, float gasket, screen gasket and main jet drain plug gasket ( this cement is gas resistant ). I hate a leaking carb and don't like to have to shut off the valve when making a short stop. You can even put a little on the threads of the gas line; it doesn't dry hard like other Permatex products. Frankly I use it at all connections from the gas tank to the carb. I use a tooth pick to apply the cement.

Works for me, maybe someone else will have a better method.

Ron
 
Ron in Quincy said:
John,

It shouldn't take but a few seconds to fill the carb bowl, not 5 minutes. I have found some of the replacment float valves to be too long when seated and it will restrict the gas flow.

Another trick I have done for many years is putting a thin film of Permatex Aviation Gasket Cement on both sides of all jet gaskets, float gasket, screen gasket and main jet drain plug gasket ( this cement is gas resistant ). I hate a leaking carb and don't like to have to shut off the valve when making a short stop. You can even put a little on the threads of the gas line; it doesn't dry hard like other Permatex products. Frankly I use it at all connections from the gas tank to the carb. I use a tooth pick to apply the cement.

Works for me, maybe someone else will have a better method.

Ron
Click to expand...

I have done the same, with Permatex #2, Ron, and it works great. A very thin film on both sides of every little gasket, with a toothpick, makes a big difference.

If using a steel needle valve (float valve) in a brass seat, I have heard that you need to tap the needle gently to seat it in the brass squarely for a good seal.
 
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