Zenith - 1 Carburetor

[Honness]

What is the GAV and where is it located? Thank you. David… by reading the posts I am thinking it’s the fuel adjusting needle in the choke driver as in the manual. If I’m wrong someone please let me know.

 

[nkaminar]

Honness, You are correct. GAV stands for Gas Adjustment Valve.

 

[Ruth]

John, Below from http://model-a.org/symptoms.html which is a good site for the Zenith carburetor. You are running too lean. If you cannot fix it they have a rebuilding service.

Mixture lean and over heating

Common Causes

• Float is set too low.
• Lower Casting Bowl Passage is restricted to Main Jet & Drain Plug.
• Compensator Jet Orifice contains dirt or rust, or is too small.
• Gasket at Main Jet is too thick or multiples are used, resulting in tip being too low.
• Main Jet Orifice contains dirt or rust, or is too small.
• Upper Casting Fuel Line Passage is restricted to Float Valve via Filter Strainer.
• Lower Casting Comp. Jet Passage is restricted to Cap Jet via Secondary Well.

To add to your list, Throttle shaft/carb body worn and sucking air in. I find this most common on old carburetors. Oversize shafts and bushings are available.

I'm not sure what carburetor the instructions are for in post #1. As far as I know there is no "packing nut" on the GAV

 

[jayvee34]

To add to your list, Throttle shaft/carb body worn and sucking air in. I find this most common on old carburetors. Oversize shafts and bushings are available.

I believe I might have updated this thread awhile back, but sorry if I did not.
I found that the main jet was undersized, and opened it up with a #63 jet
drill bit. It now works and runs perfectly @ 1/8 turn open of the GAV.
Thanks for all the help.