AC B magneto
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=170408
Printed Date: 01 Apr 2026 at 10:12am
Software Version: Web Wiz Forums 11.10 - http://www.webwizforums.com
Topic: AC B magneto
Posted By: BraedonAllisB
Subject: AC B magneto
Date Posted: 22 Apr 2020 at 8:37am
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Does anyone have or know where I can buy a new magneto for my AC b? I have a 40 model and it kicks back a little and doesn't like to start even after making the spark plugs jump gap smaller. Here is a link to how rough it starts...you have to skip ahead a little in the video, https://youtu.be/IZKHl24NeX8" rel="nofollow - https://youtu.be/IZKHl24NeX8 Do you think a magneto would fix this? Or do you think it will do better in warmer weather, in the video it was about 45 Fahrenheit? Thanks in advance all... ------------- 1940 B 19__ WD |
Replies:
Posted By: HoughMade
Date Posted: 22 Apr 2020 at 11:00am
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Well, Braedon, the first thing I have to say is that you made a fine video. The B is a great tractor and you did a wonderful job explaining everything. Second, I didn't see any significant kick when starting it. I may have missed something, but based on watching the video once, I don't think the timing is off. Would a new magneto help it start better? Possibly. A lot of people will say that the magnets in mags hardly ever wear out or that the most they will ever need is a good condenser, points and coil. Those may account for most of the issues, but I'm here to tell you that after going through all of that and then getting a mag with "recharged" magnets....huge difference. That being said, if you can hand crank start it and it runs well, which yours seems to, I wouldn't be anxious to put a new mag on it. Good ones are not cheap. That issue with your sediment bowl isn't an issue with your sediment bowl. If the floats in the carbs are set to the right level (top of the floats parallel with the mating surface of the carb body with the needle seated so you can't blow air through, upside down) and the needle and seat are good, you will not flood the engine with the bowl open. The "leave the bowl shut off to start it" is a "fix" for the floats being off or the needle and seat letting fuel leak. Shutting the fuel off at the sediment bowl to let it run out of gas like you did is a good way to keep fuel from going stale in the carb, but should not be necessary to prevent flooding (I know, I know...a lot of guys will disagree- I would like to look at their float level and needle and seat). I would tear into the carb, make sure everything is surgically clean, check the float level and needle and seat. These carbs are supper simple. Good luck!
------------- 1951 B |
Posted By: HoughMade
Date Posted: 22 Apr 2020 at 11:09am
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One more thing. I made this video a couple of weeks ago for another purpose (people complaining about hard starting with a 6v pos. ground system). When I first cranked it and it didn't start, I believe that it was because I did not allow the gas the fill up the bowl before cranking. After I paused, it lit off right away. Granted, mine is electric start. Oh, and I'm not as good at making videos as you are. [TUBE]RUHDBlDCKSs[/TUBE] ------------- 1951 B |
Posted By: Ted in NE-OH
Date Posted: 22 Apr 2020 at 1:38pm
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If the tractor kicks back when cranking , it is probably caused by improper timing. ------------- CA, WD, C, 3 Bs, 2 Gs, WC, I-400, 914 |
Posted By: Bill Long
Date Posted: 22 Apr 2020 at 2:35pm
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Don't Forget SteveNJ and his custom circuits. He is our in house electrical expert I will post this picture which has his phone number on it. Good Luck! Bill Long
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Posted By: NE GA Allis
Date Posted: 22 Apr 2020 at 2:50pm
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For starting maybe you could try the first crank with the carburetor on full choke. That’s how I always start my tractors. First crank full choke then second and sometimes third crank 1/2 choke. If I don’t full choke the first crank it usually takes more than 3 tries. Now for the running aspect, it could be the condenser. My WD kinda sounded like that before I changed the condenser out. But depending on how long it has been or if the magnets have not been recharged since new, might be a good idea to have that done. Also it may be more cost effective to send that magneto to someone from the forum for it to be rebuilt, instead of buying a “new” one. I believe some members on here rebuild and test them. Awesome video by the way! You definitely do it the right way. Can’t be too cautious around old equipment. ------------- Keeping Allis alive with: 2 B’s, 1 C, 6 CA’s, 2 WD’s, 1 WD45, 3 D15D’s, 1 D17 |
Posted By: Bill Long
Date Posted: 22 Apr 2020 at 3:31pm
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Don't forget the impulse spring. When you crank the engine you should always hear a click. That is the impulse spring spinning the armature to get spark to start the engine. If you do not hear that click we used to stop immediately. Pulled the mag and put on another impulse spring. Usually solved the problem. Without it you could get a terrible wrist breaking kick. I posted a few replies up about SteveNJ. He knows electrical and can repair your mag or can replace it. Again, if you do not hear that click when you turn the engine be very careful. Take good care of my favorite Allis Chalmers Tractor. Good Luck! Bill Long
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Posted By: BraedonAllisB
Date Posted: 23 Apr 2020 at 11:07pm
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Thanks everyone. Yeah I have the click but it just doesn't like to start. How...what is involved in recharging the magnets? Is that something that i could do (I have most of the basic mechanical knowledge) and a grandpa who restore/hotrods old cars who could help me. Like I said I need to install the new bowl, I already bought it and will see about the carb, I'm sure that I can find a few videos or my grandpa might know how. I want to try starting it here soon now that the weather is warming up. I hope to get it to a point where it starts up in the first few cranks. Thanks for all the comments on my editing ------------- 1940 B 19__ WD |