wc idle speed question
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=93332
Printed Date: 08 Sep 2025 at 4:47pm
Software Version: Web Wiz Forums 11.10 - http://www.webwizforums.com
Topic: wc idle speed question
Posted By: JM
Subject: wc idle speed question
Date Posted: 04 Aug 2014 at 8:03pm
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I have rebuilt my wc with a 45 crank and d17 piston kit. Runs great but I can only get it to idle down to 800 rpm and barely. Is this normal, book calls for 500. I have 45 carb rebuilt it has a 175 plastic venturi in it, the throttle shaft is a little loose but not bad, I have the new felt seal around it. I have checked for air leaks to no avail. Is that as low as it will go because engine is new and tight? Thanks, JM.
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Replies:
Posted By: DrAllis
Date Posted: 04 Aug 2014 at 8:30pm
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You should be able to back out/loosen the idle speed screw while pushing on the screw with your screwdriver and actually stall the engine. If you can't do that, you need to remove the carb and loosen the two throttle butterfly screws while pushing on the idle speed screw to center the butterfly in the bore. Improperly adjusted hand throttle linkage is also a concern.
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Posted By: DrAllis
Date Posted: 04 Aug 2014 at 8:41pm
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Also, the felt throttle shaft seal is inferior to the rubber seal, which I always use two rubber seals and no brass retainer. This will tighten up a loose throttle shaft.
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Posted By: JM
Date Posted: 04 Aug 2014 at 8:47pm
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Thanks DR. Yes when I try to slowly back the idle screw out I can get a fairly good idle at 800, back out a little more and it dies no matter how I adjust the air idle screw. Where should it idle? Could the big venturi be affecting it? I would think so since it is under the butter fly. I do not have the air cleaner on, maybe that would increase vacuum a little bit and change the mixture. If I put one finger across the carb air inlet at idle it dies instantly.
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Posted By: DrAllis
Date Posted: 04 Aug 2014 at 8:49pm
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Seal up the throttle shaft with the correct rubber seals, connect and air cleaner and try again. 1 1/2 turns out on the idle mixture screw is a good starting point and it should be able to idle at 400 to 500 RPM if all is right.
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Posted By: JM
Date Posted: 04 Aug 2014 at 9:25pm
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I have a oring kit, would these work for a seal? I don't know what the rubber seals are, quad ring? Right now it wants the mix screw almost all the way in- rich to idle smooth. I will give it a try, thanks.
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Posted By: DrAllis
Date Posted: 04 Aug 2014 at 9:34pm
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Marvel-Schebler carb throttle shaft seals are 70226446 from AGCO and are not an O-ring.
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Posted By: JM
Date Posted: 09 Aug 2014 at 11:23am
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Hey DR. is the throttle shaft suppose to fit in the carb body with little play or is it the seals job to hold it? Both sides of the carb seem to have a good bit of play, I am thinking of boring the other side to put a seal in and put 2 on the linkage side. Almost feel like I should bore both sides and make bushings to tighten up and put the seals in, the shaft doesn't seem to be worn. Shouldn't the shaft only have about .002 play? Thanks, JM
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Posted By: DrAllis
Date Posted: 09 Aug 2014 at 11:30am
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Ideally, the shaft would not wiggle, and yet have no drag. That would be less than .002". My adding an extra seal helps with wear on the one side where all the wear takes place. I would not add more than two of those seals because sometimes they drag on the shaft enough to affect governor response. Seems like the quality control of that seal varies from one to the next. A little WD40 lube on the shaft/seals helps.. Wear on the opposite side shouldn't effect how the engine runs (I wouldn't think) but I'm not there looking at it either.
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