Second opinion on B running issue?
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=206029
Printed Date: 19 Jul 2025 at 3:29am
Software Version: Web Wiz Forums 11.10 - http://www.webwizforums.com
Topic: Second opinion on B running issue?
Posted By: ekjdm14
Subject: Second opinion on B running issue?
Date Posted: 25 Mar 2025 at 8:22am
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Just putting this out there in case I'm missing something. My '41 B has developed a "character trait" in that it'd low idle happily all day now if I let it, even idling about 950-1000rpm it'l behave fine. Also handles a load OK for 5 minutes when started from cold. As soon as warmed up and I ask her for higher idle than that (or put any load on her) she'll run OK for a minute or so & then start lean popping/surging and eventually sputter out. Have taken my own advice on this & checked I'm not losing spark, and having a clear fuel line I've noted that after it sits a minute fuel will suddenly flow and she'll then start easily and behave exactly the same again. My first thought was sticking needle/float, but tapping the carb has no effect on anything & will still only seem to take fuel after sitting a minute. Only thing I can think of causing this is a partially clogged bowl vent, and as the fuel vaporizes more readily hot it's more prone to vapor lock then. Seem feasible? Or something else I've missed? Cheers, Dan
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Replies:
Posted By: steve(ill)
Date Posted: 25 Mar 2025 at 9:00am
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make sure the GAS TANK is vented and your not pulling a vacuum...... small piece of rust floating around in the bowl can get sucked into the main jet when EXTRA flow at LOAD... back off and the crap falls down into the bowl ?? ------------- Like them all, but love the "B"s. |
Posted By: plummerscarin
Date Posted: 25 Mar 2025 at 9:03am
| I’ve heard others mention before something may be floating in the tank and drawn in to the opening. When the tractor stops, the blockage clears itself |
Posted By: ekjdm14
Date Posted: 25 Mar 2025 at 10:09am
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You are quite correct it could be a crappy tank, it is crusty inside but I do have a standpipe hence draw fuel from 2" up, checked sediment bowl/screen and only small particles, screen clear, verified good flow through line. Definitely vented OK too. Just this minute come back inside as I had an oopsie cleaning the carb, managed to break the emulsion tube in haste. Thankfully it extracted easily, broke clean & had just enough gas left in torch to solder it back together for the moment although will be on the lookout for a replacement going forward. Of more concern now, I realised when turning the engine I seem to have dropped a good amount of compression on 2 cylinders again. Not overly worried I pulled the valve cover expecting clearances gone funky again, nope. Valvetrain still working just nice. Hopefully just washed the bores from keep stalling out, for now though need a rest the gas is getting to my head lol
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Posted By: KMAG
Date Posted: 25 Mar 2025 at 12:37pm
| Sounds like fuel lean out issue. Take off air cleaner hose to carb. Try to repeat problem condition - when begins, squirt some gas into carb opening what happens? No difference - ignition issue. Difference - carb float set too low and/or restricted fuel supply. |
Posted By: ekjdm14
Date Posted: 27 Mar 2025 at 3:46am
Air cleaner hose you say?  This poor old thing is still waiting for me to scare up an oil bowl for the cleaner so I've been running a cheap cone filter (more of a screen) for the moment. Not been in anything dusty, mind, so no danger there & it will get a real air cleaner before going to do any actual work but anyway, I did give her a spritz a couple of times and it does pick back up.Think the issue I'm into now is, the carb REALLY needs a new bowl gasket and the emulsion tube could do with replacing too so now I'm getting too much/raw gas pooling in the throat after running a second due to this. Kicking myself for damaging the carb but at the same time, she's getting so close to being a viable machine again I think she deserves a carb kit throwing into the mix. For what it's worth, I think the bowl gasket was the original issue & a chunk had broke off and got into the vent passage so it's not all for naught. Thanks all.
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Posted By: Bret (OH)
Date Posted: 07 Apr 2025 at 3:16pm
| I would suspect the Condenser. Most replacement Condensers fail prematurely. |
Posted By: ekjdm14
Date Posted: 18 Apr 2025 at 11:07am
Thanks Bret, the points/condenser are late '60s and still good  not keen on replacing with modern parts unless old stock not available. How we can collectively forget how to build a simple capacitor that can last a few years, is just sad.------------- Stuck Farmer |
Bret (OH) wrote:Posted By: Gary Burnett
Date Posted: 18 Apr 2025 at 12:08pm
That'll do it for sure
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Posted By: ekjdm14
Date Posted: 18 Apr 2025 at 12:46pm
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Well, carb gasket kit is ordered and on way so should have the carb in half decent shape whenever that arrives (From China sadly, only place that had them affordable, did look at buying American but after shipping it's over £60 for some paper gaskets and brass plugs and that was BEFORE any extra tariffs! Shipping companies really need to sort their act out in that regard.)
Also will drain & strain out the fuel a few times to try and make sure I'm not pulling down crap from the tank, although I am drawing fuel an inch or so from the bottom so not much gets into the sediment bowl currently. Will help prove/disprove if the pickup is getting plugged too though but really was acting like the bowl vent was blocked. ------------- Stuck Farmer |
Posted By: Ed (Ont)
Date Posted: 20 Apr 2025 at 8:58am
| Sounds like a bad coil. They will act up when hot. |
Posted By: jvin248
Date Posted: 20 Apr 2025 at 3:44pm
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. Find the YouTube channel Uncle Tony's Garage and watch the recent episode on distributors and points. Might give you insights. Distributor shafts can wear and wobble and need a tighter points gap to compensate. .
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