Zenith 1 Carburetor leak trouble

[700rpm]

The drain plug on my Zenith will not stop leaking. I've tried everything I can think of and can't stop that leak, even with two gaskets on the plug. I'm reluctant to tighten the plug too much because it's brass and the threads on both the plug and the carb body are very prone to stripping. I've read every document I can find on these carbs and followed all the pointers for care and cleaning. Carefully checked to confirm where the leak originates. It's the plug. Some kind of gas proof sealant might do the trick. Can someone recommend something like that or another remedy?

Note: I am running Renners jets, all gaskets are new, and the float valve setting is spot on. I am at a loss for what else to try, and will welcome any suggestions.

Thanks.

[Gary WA]

Originally Posted by 700rpm

The drain plug on my Zenith will not stop leaking. I've tried everything I can think of and can't stop that leak, even with two gaskets on the plug. I'm reluctant to tighten the plug too much because it's brass and the threads on both the plug and the carb body are very prone to stripping. I've read every document I can find on these carbs and followed all the pointers for care and cleaning. Carefully checked to confirm where the leak originates. It's the plug. Some kind of gas proof sealant might do the trick. Can someone recommend something like that or another remedy?

Note: I am running Renners jets, all gaskets are new, and the float valve setting is spot on. I am at a loss for what else to try, and will welcome any suggestions.

Thanks.

Make sure your jet is tight with one gasket! One gasket on plug tight!

[Jim/GA]

I have seen more than 1 Zenith carb with 2 gaskets on the main jet by accident. This lowers the tip of the main jet and makes the fuel level high enough in the jet to weep out of the jet tip. Then the gas runs down, out of the carb and collects on the lowest point of the carb which is the drain plug. So remove your main jet and poke around in there, make sure you only have 1 gasket on the jet or down in the hole, and that the jet is snug.

If it really is the plug that is leaking, put a light coating of non-hardening sealant (like Permatex #2) on the gasket to help it seal without having to be screwed in too tightly.

Also look at where the fuel line is screwed in, see if gas is weeping out there and running down to the plug, making it look like the plug is leaking.

[700rpm]

Thank you Jim and Gary. I’ve been reluctant to put any sealant on the plug because of its proximity to the Main jet. But I’ll approach it with caution and see what happens. I’ll report back the results.

[Benson]

Originally Posted by Jim/GA

I have seen more than 1 Zenith carb with 2 gaskets on the main jet by accident. This lowers the tip of the main jet and makes the fuel level high enough in the jet to weep out of the jet tip. Then the gas runs down, out of the carb and collects on the lowest point of the carb which is the drain plug. So remove your main jet and poke around in there, make sure you only have 1 gasket on the jet or down in the hole, and that the jet is snug.

If it really is the plug that is leaking, put a light coating of non-hardening sealant (like Permatex #2) on the gasket to help it seal without having to be screwed in too tightly.

Also look at where the fuel line is screwed in, see if gas is weeping out there and running down to the plug, making it look like the plug is leaking.

I agree with looking for more that one gasket ... Absolutely!

This is something that I see regularly ...

Caution:

to anybody who does not know about this problem ...

When removing the extra gasket or gaskets ... Do not use a hammer and screwdriver in an attempt to split the extra gasket or gaskets.

The cast iron on most castings is softer that you may think.

It is very easy to put a groove in the cast iron gasket seat ... the result is a leaking gasket surface.

[Ed in Maine]

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I work on Zenith carbs often. To get that extra gasket out of the carb I asked my dentist for help. They use a angled dental pick which has a pointed end. It was perfect for fishing out that gasket ring behind the drain plug. Don't forget that the drain plug is the lowest fitting on the Zenith. Any leaks coming from above will look like a leak at the drain plug. Ed

[Jim/GA]

I have the following tool set. I use it for things like fishing out an extra gasket, cleaning old sealant or rust from the threads of fittings, etc.

https://a.co/d/2Ba59nN

[700rpm]

Reporting back: Main jet gasket was very old and hard. Only one gasket there, no extras found. Replaced with new one. While I was in it I replaced all the gaskets with new. Cap and main jets are also in the proper position height-wise viv a vis the venture. Leak seems to have stopped. I haven’t put it back on the car yet. Ran out time.

[johnbuckley]

I find a very light smear of Blue Hylomar an excellent adjunct for sealing the gaskets. The gaskets maybe new but the castings are very old!

[nkaminar]

If you do use a sealer on the gaskets, make sure it is OK with gasoline. The silicone gasket sealers will soften in gasoline.

[Rob Doe]

Ray, I cleaned a carb once and had trouble with the gaskets leaking at the bottom of the main and cap jets. The fuel ran to the 1/16" pin hole just ahead of the jets in the throat of the carb, down to the drain plug.

[katy]

Originally Posted by Benson

When removing the extra gasket or gaskets ... Do not use a hammer and screwdriver in an attempt to split the extra gasket or gaskets. .

What would you suggest to use?

Use gaskets that are slightly soft, not too soft and not rock hard.

[700rpm]

Today’s efforts: Leak has returned. Now out the choke throat. Put new gaskets under cap and main jets. Added one thin gasket to the float jet to lower the gas level in the bowl.
I am out of ideas.

[Brentwood Bob]

Casting may be bad. Could be cracked, or porous.
Look at the thin wall between the center bolt, and the secondary well.
That was an eye opening experience for me. Put gas in the separated lower casting, wait 30 minutes, or in my case 10, and see what happens.

[700rpm]

Thanks Bob. A friend suggested that also, but I couldn’t bring myself to believe such a thing could happen. But the same idea from two people whose experience I highly respect - you and my friend- cannot be denied. I will explore that possibility tomorrow with vigor! My dad used to say, "— when you ask for advice and get it, follow it!" I should listen to his advice about advice! :-)

[Brentwood Bob]

Can't hurt.

[Fred K OR]

Ray, hello. I think the idea of getting another carb would be the best idea. I am lazy and this is what I would do. Good luck.

[Gary WA]

Originally Posted by 700rpm

Today’s efforts: Leak has returned. Now out the choke throat. Put new gaskets under cap and main jets. Added one thin gasket to the float jet to lower the gas level in the bowl.
I am out of ideas.

Send to me and I will go thru it FREE of charge just postage.

[700rpm]

Hi Fred. I’m looking at one on the MAFCA classified site for $222. I may go for it. I used some permatex 2 on the plug this morning. We ‘ll see what happens.

[Rob Doe]

Ray, check your jets. Do they have the dished, inside chamfer at their tips?

When my jets were leaking at their bases, as suggested by H. L. Chauvin, I bought a set of Bratton's black gaskets. They are of a different material. I have the correct tool from the vendors for tightening them and they sealed.

Make sure the 1/16" hole in the throat bottom is open.