Farm Equipment - FMX-4B3 magneto original on a B?

Print Page | Close Window

FMX-4B3 magneto original on a B?

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=7793
Printed Date: 03 Nov 2025 at 10:56pm
Software Version: Web Wiz Forums 11.10 - http://www.webwizforums.com

Topic: FMX-4B3 magneto original on a B?

Posted By: wjohn
Subject: FMX-4B3 magneto original on a B?
Date Posted: 07 Feb 2010 at 9:02pm

I was just wondering if the FMX-4B3 magneto that is on my Allis Chalmers B is original?Most everything I've found seems to say that the FMJ-4B3 mag is what it should have, but I have seen several different sources mentioning different magnetos from the factory. My tractor is a 1939 and the FMX mag on it has a grounding tab. It's definitely possible that someone replaced the mag on it but I was just curious.

Replies:

Posted By: morton(pa)
Date Posted: 07 Feb 2010 at 9:09pm

I was told by a very well known mechanic that works on older tractors, that the FMX was one of the very last magnetos made by Fairbanks-Morse and was made as a replacement magneto. I was also told the FMJ-4B would have been the stock mag for the B coming out of the factory. I think I was told the FMX was made in the late 50's and early 60's right before they stopped producing mags. So it is most likely that it was replaced.

Posted By: GreenOrange
Date Posted: 07 Feb 2010 at 9:51pm

Morton is right, the FMX was one of the last. Your '39 B is right about the time they went from the FMK to the FMJ - I suspect it originally had a FMK.
-John

Posted By: wjohn
Date Posted: 07 Feb 2010 at 10:00pm

Thanks to both of you for the info. I have been wondering whether it is worth trying to keep the tractor original, but I think I'm just going to get it running and use it for a few years and not worry about factory-correct parts.

Someday I'd like to accurately restore it but for now practicality takes priority. I'd have to find a mag, front rims, a seat... not terribly hard (well riveted rims might be), but not worth the money at this point. As it sits now, it should function great (once I get it running, haha!).