Slight Carb Leak

[Mulletwagon]

Over a period of a few hours, is it somewhat common for a Zenith carb to drip slightly with the tank valve open ? Is dripping less likely with an all metal float valve or a viton tipped valve ? Is it unreasonable to expect no leaking at all over an extended period ? Pretty sure my problem is the float valve rather than a dash mixture needle leak.

[daren007]

Yes

[30 Closed Cab PU]

Leaking like that is not uncommon, sometimes difficult to stop. Try the Viton Valve and running 4 oz. of Marvel Mystery oil every Tank of gas. Helps keep the Viton valve conditioned .


Also recommended is to take the Viton valve apart before install, and clean/inspect thoroughly. Sometimes machining debris is not properly cleaned out of the seat area.


If you are replacing the float valve, also set the float height before reassembly and installing the carb


I have yet to do this , but will be soon, as I have more than a small few drops leak.


If it is leaking with the fuel shutoff turned off, you also have a leaky shutoff, you should also fix that. Order a replacement fuel shutoff from Brattons, US made guaranteed for 3 years. Some of the other venders sell import shutoffs that leak new out of box.


And as long as you may have the fuel shutoff out, if not installed, add a Fuel Tank Filter Screen(Pencil fFilter). When installed it sticks out the top of the shutoff up into the gas tank. Might as well clean out the gas tank at the same time.


Perhaps you know the above, but mentioned it all to be through.

[whirnot]

I don't know how common, but it isn't right.
You may forget to shut the tank valve once in a while, do you really want gas dripping out?
Mine don't leak.

[johnbuckley]

yes,eventual seepage is common - the float valve is a metering device not a shut off valve and should recognised as such.
I have encountered problems both with metal, grose jet and viton so now have no preference.

[30 Closed Cab PU]

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Originally Posted by whirnot

I don't know how common, but it isn't right.
You may forget to shut the tank valve once in a while, do you really want gas dripping out?
Mine don't leak.

To elaborate - my meaning is it not an uncommon issue, and it sometimes can be a struggle to stop the dribble. 10 gallons of gravity fed gas is asking a lot of the small metering/float valve. Some just live with it, others do not because they do not want the smell of gas in their storage/garage or the possibility of fire/explosion, when forgetting to turn off the Fuel Shutoff.

[Railcarmover]

If your float level setting is incorrect it can leak out of the jet.A grose style float valve is superior to a viton needle.

[JD 1931]

The Zenith carb for the model a is an updraft and sometime will leak a small amount when shut down. Every time I turn the key off I shut the shut valve off and when shutting down for the day I shut the valve off and let engine die. If you do this don't forget to shut key off when done….

[WHN]

We turn the gas valve off every time we turn the car off.

Gravity is working 24/7 365, you can’t get away from it. Enjoy.

[larrys40]

Originally Posted by Railcarmover

If your float level setting is incorrect it can leak out of the jet.A grose style float valve is superior to a viton needle.

If set to high it can leak and top over the cap and main jets either way. If course there’s are many opinions but on the whole the gross jets have their own issues of sticking and not sealing well. This is just my experience. I buy the vitons about 12 or 15 at a time and check them with my hand vacuum pump to see if they hold . If 7 out of 10 do that is about it unfortunately. I do agree that a good shutoff either way should be inline and seal.

Other things that can cause it are cap or main jets and gaskets not snugged and or sealing well which will cause gas to weep and be in the throat.
Use a finger or two in the throat to see if fuel is present there.

[Purdy Swoft]

Sometimes the reproduction cap and main jets can be too short . If the cap or main jet is too short , as in below the level of the gas in the bowl of the carburetor , it will continue to drip out the back of the carb if the cut off valve is bad .