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Allis Chalmers Discussion Forum
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1941 AC B (carb question)

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farmerwannabe

11-07-2005 16:45:59




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Well guys, here's another question for you. I got the B running really well..for a while. It starts and runs great for about 5 minutes or so, then it starts to sputter and stalls. It'll fire right up and run well for a short time, then start to sputter again. When it starts to sputter, if I put the choke on all the way, it will keep running. It'll run rough, but it'll keep running.
Obviously, this is something with the fuel delivery. I'm guessing it's not getting enough fuel and starts to empty the carb, that's why it'll keep running with the choke on. (my guess anyway). If I keep the fuel petcock on the sediment bowl on, the carb will overflow and be a real pain to try and restart. Keeping these things in mind, and the fact the carb was supposedly rebuilt soon before I bought the tractor a few months ago, what are your thoughts? There's a set screw on the top of the carb, but I'm not sure if this is an idle screw or just what it is. I could really use some suggestions as to what you think I should do to get this running a little more reliably for plowing the driveway this winter. Thanks again for all the help in the past and in advance for the help regarding this problem.

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Dick L

11-08-2005 12:50:28




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 If Your Going To Rebuild in reply to farmerwannabe, 11-07-2005 16:45:59  
If you are going to rebuild your carburetor and you do not have a drawing you might want to print the one below.
Nine times out of ten you will find the leak thru your carburetor having to do with the float valve. Most of the time it will be a speck of rust or such. I have not had good luck with the rubber/plastic tipped float valves in the past. I have rebuilt a few in the near past that worked out but back eight or nine years ago I had over half fail. I save every thing that I take out if it looks like there mignt be any use left in what ever it is. The ones that failed I replaced with used, redressed solid brass float valves. The last rebuild kit I purchased had a solid steel float valve. For tractors that set a lot I am not sold on the steel float valves ether, but it did not leak. A drop of water standing at the tip will start its own supply of rust.

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jeffalex2

11-07-2005 19:50:23




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 Re: 1941 AC B (carb question) in reply to farmerwannabe, 11-07-2005 16:45:59  
you've definately got a float problem. My B will sit forever and not flood out like yours. It's usually a simple adjustment but it has to be made with the carb off of the tractor. The float and needle are adjusted such that the needle valve stops flow into the carb when 1 5/16 inches is measured from the bottom of the float to the bottom of the carb body. I don't have my manual handy, but, I'm pretty sure that's the measurement.

As far as needing to choke to keep running, that also could be float related, but sounds more like supply blockage (rust in tank, gunk in line, etc.) Also could be clogged jets in the carb...maybe got some dirt in there when you swapped out sediment bowls...?

The Allis carbs were designed to have an idle mix adjustment, but ran off of a preset mix once off of idle. The screw is for idle adjustment and has little affect at operating speeds.

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old

11-07-2005 22:03:14




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 Re: 1941 AC B (carb question) in reply to jeffalex2, 11-07-2005 19:50:23  
@ things I would like to ask you. You say allis carbs. Well allis didn't make the carb for the B its a Zenith. Also as per the book Turning the power adjust needle towards its seat leans the mixture. So then there is a main jet on them isn't there or is the book wrong??/



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CH

11-08-2005 15:05:14




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 Re: 1941 AC B (carb question) in reply to old, 11-07-2005 22:03:14  
They actually had both. One of my B's has an adjustable mixture and the other is a fixed jet.



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mace56

11-07-2005 17:51:24




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 Re: 1941 AC B (carb question) in reply to farmerwannabe, 11-07-2005 16:45:59  
My B card seems finnicky too. I suspect dirt keeps working thru and holding needle off seat. I have though about a little inline filter to see if that would keep it running more consistently.
Actually mine usually runs fine but i have to shut off at tank when parked or it will leak and be hard to start.



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BCnT

11-07-2005 17:40:55




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 Re: 1941 AC B (carb question) in reply to farmerwannabe, 11-07-2005 16:45:59  
dont take it for granted it was rebuilt right...kits are cheap...get one and go thru carb yourself and pay close attention to float and needle n seat under float...thats the only 2 things that will cause those problems



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old

11-07-2005 17:40:45




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 Re: 1941 AC B (carb question) in reply to farmerwannabe, 11-07-2005 16:45:59  
That screw should be your idle adjustment. Is there a screw on the bottom or one that sits at about a 45 degree angle, if so thats your main jet. I don't remember for sure if a B had one or not been to many years since I played with one. As far as your problem with gas comeing out of the carb that menas that the float needle and or seat or float have problems. You might have a bad float or bad needle. Or you might have some junk in the seat which would also cause the problem. Also just because it was rebuilt doesn't mena it was done right. I've seen more then one rebuilt carb not work as it should. I've even been there done that may self and I rebuild carbs all the time and have had to redo more then one.

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farmerwannabe

11-08-2005 08:36:30




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 Re: 1941 AC B (carb question) in reply to old, 11-07-2005 17:40:45  
Well, it sounds like my best bet is to take the carb off and rebuilt it. Any hints as to how to get started? Assuming I have the carb sitting on the table in front of me, how should I get started? Thanks again for the advice.



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old

11-08-2005 08:41:45




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 Re: 1941 AC B (carb question) in reply to farmerwannabe, 11-08-2005 08:36:30  
First get a kit, it will have a picture of the carb and where all the parts go. Also get a can of beamans carb/parts cleaner. Get the gallion round can not the square/retangler can. The round can will have a soaking basket in it. Then carefully take the carb apart, don't put any plastic parts in the cleaner because they will not be parts any more if you do. Let it sit in the cleaner over night or 24 hours or so. Also pick up a couple cans of spray carb cleaner to help you blow out the small places in the carb.

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farmerwannabe

11-08-2005 15:31:22




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 Re: 1941 AC B (carb question) in reply to old, 11-08-2005 08:41:45  
Thanks Old...any other suggestions so I get it done "right"?



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old

11-08-2005 16:25:33




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 Re: 1941 AC B (carb question) in reply to farmerwannabe, 11-08-2005 15:31:22  
When you put it back togeather be sure to get the float needle seat good and tight, and also if the kit comes with a rubber tipped needle drop it in the seat after you install the seat and tap on it a couple times with a hammer etc. Not very hard just a lite tap. A hammer maybe to big but a cheisel end etc works fine.



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farmerwannabe

11-09-2005 17:17:44




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 Re: 1941 AC B (carb question) in reply to old, 11-08-2005 16:25:33  
Thanks again Old....I"ll get on that this weekend!



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old

11-09-2005 17:55:56




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 Re: 1941 AC B (carb question) in reply to farmerwannabe, 11-09-2005 17:17:44  
I wish you luck.



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farmerwannabe

11-10-2005 08:47:04




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 Re: 1941 AC B (carb question) in reply to old, 11-09-2005 17:55:56  
I think I'm a little gun shy when it comes to the measurements for the float. What's the best way to go about that once the rebuild is done?



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old

11-10-2005 08:51:54




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 Re: 1941 AC B (carb question) in reply to farmerwannabe, 11-10-2005 08:47:04  
The instuctions that come with the kit expalain it very well and you shouldn't have any trouble if you read them.



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