Re: Sediment bowl filter/Idle adjust screw

Posted by Mike Flanagan on November 25, 1997 at 09:34:30

In Reply to: Re: Sediment bowl filter/Idle adjust screw
posted by MRR on November 25, 1997 at 07:37:09

Your problem is probably a run rich to start with. When you open the idle circuit you introduce more gas into the equation and it has so much fuel it cannot function. The main jet is probably the culprit. One question is where is the mixture control (choker rod) set while all this is going on. Another question is what is the altitude where you are located. All these things affect the operation of the carb. Buy the book on Carbs written by Paul Moller. Once you understand the opeation of the little carb you will be able to balance it accordingly.
The Main Jet should be .035 dia. this is easily checked with the carb on the car. Remove the drain plug (gas off) and carefully insert a screw driver into the hole the plug came from. The plug is the 1/2 hex on the bottom of the carb. The jet will screw out and into your hand. Check the diameter of the orifice. Anything over .035 is ng. Repro jets have a bad habit of being to big. Next problem is float level. Must be correct and is difficult to set without a sight gauge. Snyder's has them for $4.00.
Once your carb is up to snuff you should be optimum I try for is normal operating at local elevation with 1/4 turn on choker rod, and from 1 to 2 1/2 turns open onm idle with idle set at whatever speed you prefer. The more idle speed you have using the thumb screw (which opens the throttle) the less effect the idle circuit has because you are bypassing with the throttle.
Once you achieve optimum,and you will, you will have room to climb to altitude and reduce the mixture control accordingly. If you are driving around at sea level with the mixture off you have no adjustment as you climb and run rich is inevitable.
God Speed Under 50.
The Model A Fool.
: : I'm not sure that this is the exact answer you were looking for but Walt Bratton sells a glass sediment bowl micro-filter part # A 9160-F that may work for your sediment bowl (assuming you have a glass setup).Call his establishment at 1-800-255-1929.
: If you are getting that much of an effect out of opening your needle valve, you may have a problem with the the needle seat.Both the needle and seat are easily replaced on a Zenith.That is what you have isn't it?If that doesn't work then it could be one of the jets is dumping so much fuel that it is flooding out.The Zenith is an easily rebuilt carburetor.Sometimes it takes some experimentation to find the right fix for the right carburetor.That's part of the enjoyment of the A.On the other hand, if it runs ok with the needle closed, leave it alone until it needs to be fixed.My double venturi Zenith works very well with the needle closed.

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