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Old 04-01-2020, 06:55 PM   #1
Marcus
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Default Carburator Update

Well, replaced the carb with a supposedly rebuilt unit: never thought (I know, rookie!) to check if the gav would turn prior to installation - and now discovered it won't turn either direction. Gav on the old carburator turned perfectly, so the bind must be in the new one. Any suggestions for me? I am hesitant to force it to turn.
Also, any recommendations to whom I should send the old one for a quality rebuild?
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Old 04-01-2020, 07:04 PM   #2
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Default Re: Carburator Update

If you take the choke control elbow shape lever, off then the GAV top part will slide up and off. Spray some penetrating oil or something similar to lub the threads and then put the top part back on, turn counter clock wise after letting it sit a few minutes. Should loosen up. If not then it may have to come apart with a wrench but the brass is fragile so don't force anything, just keep spraying down in there.
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Old 04-01-2020, 07:13 PM   #3
James G.
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Default Re: Carburator Update

All good advise. The only thing I'd add is if you do use a wrench on the brass fitting that you make sure to use a box wrench of proper fit/size, the brass is indeed soft.
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Old 04-01-2020, 07:51 PM   #4
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Default Re: Carburator Update

I think what has happened is someone set the GAV overly tight, the needle has now "galled" to its seat, and preventing relative motion.

The GAV needle passes through the housing part you see. With the driver off and removed you'll see the half circle of the GAV Needle inside the housing.

Using the box wrench (preferably 6 pt. You may want a choice of No. 10 metric and 3/8 - one or the other will fit) if you remove the housing, you get both housing AND the needle.

With the two removed you might be able to use a wrench or vise to hold the housing and turn the needle with the driver. You may see the "gall" on the pointy end - this can be cleaned up with emery cloth.

Some Zenith have a brass "seat" for the needle to work against. Others have a cast iron seat. Both are prone to this sort of galling. Removing the entire GAV assembly gets you past this post haste.

Joe in NH
Who only yesterday had the same issue on the identical part - and ended up "crushing" the thin portion of the GAV housing with a pair of vise grips simply to remove it. In my case a torch helped to a successful removal. (Brass and cast iron ALWAYS are easier to remove after heating.) The parts are readily available but you may need to do some "fitment" of the needle to the housing to get the proper degree of resistance to turning.
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Old 04-01-2020, 07:53 PM   #5
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Default Re: Carburator Update

You may want to take a look at your adjusting needle O.D. I had the same issue and ended up using my old needle.Gas Adjusting Valve.jpg
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Old 04-01-2020, 07:59 PM   #6
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Default Re: Carburator Update

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Marcus I would call JR. He rebuilds carbs and likes to help people in the Model A hobby. He might be able to help you fix the carb yourself.
900-748-8299
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Old 04-02-2020, 08:11 AM   #7
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Default Re: Carburator Update

tuesday

Last edited by Benson; 04-11-2020 at 08:19 AM.
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Old 04-02-2020, 08:17 AM   #8
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Default Re: Carburator Update

Quote:
Originally Posted by Benson View Post
DO NOT use this phone number...

Calling 900 area code will result in a charge to your phone bill! $50 $100 whatever they want to charge!


1 900 numbers explained
US telephone numbers starting with area code 900 are also known as Pay Per Call numbers or Information Services. These telephone numbers are exclusively used by companies providing a service, an information, etc. Basically you call the (1) 900 number and you get charged either a per call or per minute fee in addition to the regular rates charged by your long distance company. You are provided the service offered by the 900 company over the phone. Some services available this way are:
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Avoid unwanted charges
While there are many 900 companies providing a legitimate service and not trying to hide their fees from consumers, some companies do try to lure those unaware of what a 900 number is into calling them without clearly stating all the charges. You may receive a notification of winning a trip, or a contest you've never signed up for and be asked to call a 900 number to receive your prize. These are usually sneaky attempts to make you pay for virtually nothing. Our advice: before calling a 900 number you should know all the details about what service you're supposed to get and all the charges involved. Also, try to educate children regarding calling pay per call services for they are the easiest to get lured into calling pay per call numbers. Other things you should know:
You can block 900 calls by contacting your phone company
Pay per call charges must be separately listed on your telephone bill
Your telephone company can not cancel your service if you refuse to pay 900 pay per call charges
Sorry the number is 903, not 900. My mistake. He now has a web site.
https://jmacarbs.com/
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Old 04-02-2020, 10:41 AM   #9
Joe K
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Default Re: Carburator Update

Quote:
Originally Posted by SoCal_Alden View Post
You may want to take a look at your adjusting needle O.D. I had the same issue and ended up using my old needle.Attachment 426024
It is possible to remove the circlip and "bend" the fingers by pushing an awl down the GAV housing throat. One has to be careful not to push too far lest one break off a finger.

The GAV housing CAN be used without the circlip if it is too tight on the needle. The circlip can be substituted with a SMALL o-ring for greater tension than bare fingers alone.

And - even if a finger gets broken off, that may be just the right amount of tension on the needle shaft with what remains - with or without the circlip. I'm currently broken but using the metal circlip.

You have to play around with it and get the right "feel" to the knob. You want it easy to turn, not galling, but not so loose that the GAV moves by itself under the vibration of the engine.

In the Model B carburetor, Ford went with a washer and spring which holds tension on the GAV needle shoulder - a different setup entirely.

Joe K
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Old 04-02-2020, 12:43 PM   #10
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Default Re: Carburator Update

Some things

Last edited by Benson; 04-11-2020 at 07:52 AM.
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