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b carb

Printed From: Unofficial Allis
Category: Allis Chalmers
Forum Name: Farm Equipment
Forum Description: everything about Allis-Chalmers farm equipment
URL: https://www.allischalmers.com/forum/forum_posts.asp?TID=30096
Printed Date: 05 Mar 2025 at 1:27pm
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Topic: b carb

Posted By: DonDittmar
Subject: b carb
Date Posted: 02 May 2011 at 6:44am

Got the surge fixed, but something is wrong in the idle circut of the carb. It runs rough at idle, runs great on the dyno under load, just idles like crap. I have had the crab off 3 times and cleaned it out/check float adjustments. I did notice that if you run the idle screw all the way in or back it all the way out there is no change.

Does anyone have a good used Zenith carb off of a B?

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Experience is a fancy name for past mistakes. "Great moments are born from great opportunity"

1968 D15D,1962 D19D
Also 1965 Cub Loboy and 1958 JD 720 Diesel Pony Start

Replies:

Posted By: cmsmoke
Date Posted: 02 May 2011 at 7:30am

From what you describe, the idle circut is more than likely clogged, don't give up on your carb. yet.

Make sure the low speed jet, in the top of the carb is opened straight through. I had the same problem with my "C" Zenith carb. I also had mine off before and missed this. I took it off yesterday and soaked the jet, then did some probing with a torch tip cleaner. There was chunk of something in there that had to be in there for years. I thought it was solder and was supposed to be that way. Now my air screw works and I can get my idle down to below 400, if desired.

If you pull your choke out slowly, will it come to a point where the engine smooths out nicely? This will be another tale-tale sign that it is running lean.