Carb Settings for Allis G
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=138848
Printed Date: 29 Apr 2025 at 11:34am
Software Version: Web Wiz Forums 11.10 - http://www.webwizforums.com
Topic: Carb Settings for Allis G
Posted By: bluegrama
Subject: Carb Settings for Allis G
Date Posted: 28 May 2017 at 12:13pm
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Hi All, I just picked up an Allis G which I'm hoping to put back to work as a row crop cultivator. I did a bunch of basic maintenance and now have it running, but it seems like I'm just not getting enough fuel to the engine. The engine surges/hunts pretty hard when cold, and will just stop running when it warms up unless I hold the choke about half closed. This keeps it running and smooths the surging. The surging is present both idle and full throttle. I've played a bit with the one (idle) mixture screw, and that doesn't seem to do much. There is no screw to adjust the mixture under load. I just rebuilt the carb, so I'm now wondering what I can do to get this running smoothly. I don't think there's an air leak (I put a new throttle shaft in the carb), and I'm pretty sure I got the passages in the carb clean. I did replace the float as well, and set it to 1/4 inch from the gasket. When I did the carb work, I also replaced the plugs, and cleaned up the fuel filter. Compression seems good (around 80 PSI at 6000 feet). The bowl seems to fill quickly when I open the gas valve, so I think I'm getting gas to the carb. What would you try next? Are there issues with things other than the fuel system which may be causing my symptoms?
Thanks for your help, George
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Replies:
Posted By: Gerald J.
Date Posted: 28 May 2017 at 6:00pm
There could be a vacuum leak somewhere on the intake manifold, either at the block interface or the carburetor flange. There could be junk in the fuel line, primarily varnish to restrict fuel flow. There could be a dirty screen at the inlet elbow to the carburetor. The main jet passage could be not as clean as needed.
Ignition timing could be delayed from not quite the right setting or from rusted or broken centrifugal advance parts inside the distributor.
Gerald J.
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Posted By: Dick L
Date Posted: 28 May 2017 at 7:56pm
This has a non adjustable power jet. After you have the idle properly set for idle changing the idle screw then takes the away from the proper idle setting.
I is most likely a fuel restriction some where from the tank to the manifold. I would remove the fuel line and sediment bowl and make sure I had good flow thru all of that first by checking all the passages in the sediment bowl. Crappy fuel tanks are a problem many times.
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Posted By: Chris (swIA)
Date Posted: 29 May 2017 at 7:30am
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Take the fuel tank off and remove the shut off and clean it and the tank outlet. Mine was doing the same thing and it was almost plugged.
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Posted By: Fred in Pa
Date Posted: 29 May 2017 at 7:54am
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I worked on a few that I opened up main jet just a couple thousands .Check gov. also
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He who dies with the most toys is,
nonetheless ,still dead.
If all else fails ,Read all that is PRINTED.
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Posted By: TramwayGuy
Date Posted: 29 May 2017 at 4:44pm
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Don't overlook a restricted exhaust as well. Not real likely, but it could happen.
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Posted By: bluegrama
Date Posted: 29 May 2017 at 11:27pm
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Thanks to everybody who replied. I really appreciate the help and now have a few things to look into. I looked at it a bit today and made some definite progress: I now have it idling well, and it no longer stops running when it gets hot, but I'm still getting the surging at full throttle. The improvement seems to have been from a combination of fixing one of the spark plug wires which wasn't well seated in the distributor, and also from messing with the timing, as Gerald suggested. I didn't mark where it was, but I think it was a bit retarded, and seems to be happier now that it is a bit more advanced.
I still have the surging issue at full throttle, though. I think I've ruled out fuel delivery issues to the carb - if I take the drain plug out of the carb, I get a small but steady stream of fuel out of the drain. I don't really know, but it seems like enough flow to run the engine. So if there is a fuel issue, it seems like it must be downstream of the carb bowl. I also ruled out an air leak by spraying carb cleaner around the carb and manifold with it running. The suggestion about a restricted exhaust is interesting. My muffler does look smaller than stock, so I'll try running without it if I can actually get it off...
On the electrical side, I verified that the firing order is correct. And I don't think the full-throttle surging can be due to timing now, as I played with the timing at full throttle with no improvement. The point gap is correct (0.02 in).
I also checked out the coil. The primary resistance seems reasonable (1.8 ohms), but I kept measuring the secondary resistance at infinity, which sounds suspicious. I'm a bit surprised the engine runs at all with that reading. While the tractor was never converted to 12v, I do know the previous owner has started it using a 12v battery at least a few times, so I'm wondering if that could have damaged the coil. Should I just get a new coil? It looks like I can just pick one up at Napa (part number ic7?).
Thanks again, George
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Posted By: Chalmersbob
Date Posted: 30 May 2017 at 11:21pm
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There are instructions in the manual about surging. There is a screw in the side of the timing gear cover that is used to control the surging. Bob
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4 B's, 1 C's,3 CA's, 2 G's WD, D14, D15, B-1, B10, B12, 712S,
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Posted By: bluegrama
Date Posted: 27 Jun 2017 at 4:28pm
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Thanks again for all of the suggestions. I finally got around to working on the tractor again, and I've now got it running well, so I figured I'd post an updated just in case somebody else runs into a similar issue.
I ended up replacing the coil because of the resistance reading, and it may have helped just a bit, but not a great deal. I also did play with the screw on the governor to control surging, and even with it all the way in, I was still getting surging at full throttle. I then tore down the carb again, cleaned it and adjusted the float height. It looked like there might have been just a speck of something restricting the main jet. Now that I've put it back together, it runs like a champ. So I think the winner was the blockage in the carb jet.
Now I just need to put it to work cultivating...
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Posted By: CrestonM
Date Posted: 27 Jun 2017 at 4:37pm
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My G used to run well just sitting idling, but when I'd put it in gear and drive off, the engine would start surging, and the only way to stop it was to stop and slow the engine down all the way. Grandpa fixed it for me back in 2009 by putting a second governor spring on. That helped. It's not an "official" governor spring, just something he had on hand. It's been fine ever since.
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