Farm Equipment - Zenith carb adjustment

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Zenith carb adjustment

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Category: Allis Chalmers
Forum Name: Farm Equipment
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URL: https://www.allischalmers.com/forum/forum_posts.asp?TID=35669
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Topic: Zenith carb adjustment

Posted By: bigjohng2
Subject: Zenith carb adjustment
Date Posted: 17 Aug 2011 at 5:45pm

I just helped a friend work on a WC with a zenith carb which had been rebuilt. We got the tractor to start ,but it would run for only 30 seconds or so then quit as if out of gas. What is the correct way to set the float? Also where are the best needle settings? I started at 1 1/2 turns on each one. We have fresh gas and the gas does seem to flow freely to the carb. Is there anything elese I need to check which would allow it to run then die? Thanks for any help.

Replies:

Posted By: Chalmersbob
Date Posted: 17 Aug 2011 at 10:36pm

it should have a plug in the bottom of the carb. remove it with a bucket under it, and let the gas run for a while to check flow. Problem could be in the gas tank.

To set the float, you must remove the carb, dismantle it and turn it upside down. The float should be about 1/4" above the gasket face. approximately level. Bob

Posted By: beeman
Date Posted: 18 Aug 2011 at 8:17pm

Vent open in gas cap? Just a thought.

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1949 B 3930 Ford- Have owned other Orange ,green,red,yellow,dark green tractors and equipment.

Posted By: Rogers
Date Posted: 19 Aug 2011 at 7:14pm

For a Zenith carb you start 1-1/2 turns out on the upper air needle and 4-1/2 turns out on the lower gas needle. This should be good enough to allow the engine to run.

After starting open the engine to about half throttle and let it run for a minute to warm up. Close back on the lower main gas needle until the engine begins to run lean starving for gas.

Then start opening back up on the lower gas needle until the engine begins running rich
keeping up with how many turns you opened it back up. Leave the main gas needle set half way between lean and rich.

I have found that the final main gas needle adjustment is about ¾ to 1 turn open from where the engine started starving for gas, and the air needle ends up staying at 1-1/2 tuns out. If your problem is the carburetor adjustment this should get you going.

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Think for yourself and be your own expert. Be willing to change your mind; however, willingness to change your mind doesn’t mean that you will. Blindly following any path is the pinnacle of insanity.

Posted By: bigjohng2
Date Posted: 20 Aug 2011 at 9:12am

Thanks for all the help. We are going to try to get her running again today.