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Old 03-08-2018, 08:19 PM   #1
JD 1931
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Default Zenith LEAKS after rebuild

I have rebuilt many Zeniths carbs. this one has me. After I rebuild them I test them on my original 31 model A. I bolted it on, turned the fuel on and in about 3 seconds she floods gas out without even starting, leaks when running also. I changed the float valve to a new one that does not leak, checked the float level, float good with no leaks, gaskets good, checked all passages, checked GAV, checked jets, filled bottom half when apart and did not leak, assembled it and leaked. float valve looks to be seating with float . Had it off and on about 8 times. Need advice.....Thanks JD

Last edited by JD 1931; 03-08-2018 at 11:38 PM. Reason: correct
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Old 03-08-2018, 08:36 PM   #2
duke36
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Default Re: Zenith LEAKS after rebuild

viton tipped needle ?
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Old 03-09-2018, 05:16 AM   #3
johnbuckley
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Default Re: Zenith LEAKS after rebuild

1) switch off fuel and if remove residue fuel on outside body of carbs with dry cloth, paper towel or airline switch on fuel and very very closely observe the carb ... often when fitting a carb the leak is from the inlet pipe where it fits into the body ( #11 on list below), If it's not that simple run thorugh the rest of this list ...
Zeniths: Causes of leaking
Problem: Remedy
1 Leaking/loose float valve gasket: Tighten/reseal/replace
2 Leaking float valve: (or crud stopping it sealing) Replace (or clean up if possible )
3 Friction on float hinge: Loosen
4 Incorrectly set fuel level: Re-set
5 Hole in float: Repair or replace
6 Too many gaskets on main jet Check
7 Cap jet or main jet too short: Replace
8 Leaking/loose gasket at main jet: Tighten/reseal/ replace
9 Leaking /loose gasket at cap jet: Tighten/replace
10 Leaking or loose GAV housing threads: Tighten/ reseal/ replace
11 Leak at fuel inlet union: Tighten/reseal/replace
12 Loose/leaking gasket at strainer: Tighten/reseal/replace
13 Loose/leaking gasket at drain plug: Tighten/reseal/replace
14 Cracked housing/leaking passage plugs: Repair or replace

1-7 will generally manifest as poor running.
8-14 will generally not affect running unless there is excessive leaking.
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Old 03-09-2018, 10:26 AM   #4
barnstuf
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Default Re: Zenith LEAKS after rebuild

Snyder's A-9564-S is a float valve shim kit of thin gaskets to get a more exact float level setting. The have solved leak problems for me.
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Old 03-09-2018, 10:32 AM   #5
Will N
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Default Re: Zenith LEAKS after rebuild

Make sure that the float is free to move in the bowl. I had interference from a ridge in the bowl casting that was causing the float to hang up.
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Old 03-09-2018, 02:35 PM   #6
Ron in Quincy
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Default Re: Zenith LEAKS after rebuild

If the housing gasket gets wet when you turn on the fuel the leak will be the fuel line connection ; the gas will run to the back of the carb, run down and leak off the mounting bolt.

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Old 03-09-2018, 07:44 PM   #7
TJMack
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Default Re: Zenith LEAKS after rebuild

Welcome to the club! This is a common problem. We've had some good discussions about it lately. I've been chasing the same thing for weeks. Look back at old threads like the one that I started titled "Carburetor Float Valves" and especially the one started by Fixitphil titled "The Zenith Carburetor". That one has some excellent links to very useful information. It's very frustrating, I know.
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Old 03-09-2018, 07:53 PM   #8
Ed Saniewski
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Default Re: Zenith LEAKS after rebuild

Are you sure where the leak is coming from? I chased a leaky carb for a week, taking it apart many times, only to find the leak was coming from a brass plug in one of the passage ways.
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Old 03-09-2018, 09:19 PM   #9
Bikerider58
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Default Re: Zenith LEAKS after rebuild

How is the float valve landing on the float? If rough, the needle could be getting caught and kept from moving.

New float valve? Check for stuff, grit or metal bits from matching it valve. Newer stuff seems to be not as good in recent lots.
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Old 03-10-2018, 03:37 PM   #10
Brkile
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Default Re: Zenith LEAKS after rebuild

I have the same problem. The carb body gasket gets wet. My question is, how much can the fuel line fitting be tightened before damage is done ?? Is it better to replace the brass ferrel (sp) or is there a gas-resistant sealer than can be used ?? (Thanks for letting me piggyback on this thread)
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Old 03-10-2018, 04:25 PM   #11
johnbuckley
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Default Re: Zenith LEAKS after rebuild

use a small spanner ( wrench, to you guys!) for tightening the nut and don't put your weight on it.- no idea what torque . Best to have a new ferrule .they are cheap enough and a new line c/w ferrules is only a few dollars . I know many disapprove ... but I find that quality PTFE tape over the olive is a good method for eliminating minor problems ... .. perhaps the PTFE tape over here is more fuel restistant??
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Old 03-12-2018, 07:32 AM   #12
JD 1931
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Default Re: Zenith LEAKS after rebuild

I have tried all possible cures with no results and now I am going to build another top and try that, I guess that is what you get sometimes when buying old junker carbs to rebuild...Thanks to all that responded, JD
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Old 03-15-2018, 05:55 PM   #13
Fred K-OR
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Default Re: Zenith LEAKS after rebuild

I had one leak where the GAV "housing" bolts into the lower part of the carb. It had a crack where the "housing" screws into the lower part of the carb.
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Old 04-14-2018, 03:00 PM   #14
fordfixer
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Default Re: Zenith LEAKS after rebuild

The seat for the gas line could need honing. I've seen several that would leak. The repair books tell how to set the stone up for this. I've also seen where someone has added solder to the Ferrell so when they tighten it down it seals the line
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