Farm Equipment - 1939 B Mag

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1939 B Mag

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=17921
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Topic: 1939 B Mag

Posted By: Ole Shovel
Subject: 1939 B Mag
Date Posted: 08 Sep 2010 at 2:05pm

Did a 1939 B come originally with a FM-J4B3 mag or a RV 4 mag or a Wico C or other? Thanks.

Replies:

Posted By: CTuckerNWIL
Date Posted: 08 Sep 2010 at 2:22pm

I would guess 90% of em sold in the USA had the FM-J4B. I never heard of a B with a FM RV4 on it but I suppose it could have happened.

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Lena 1935 WC12xxx, Willie 1951 CA6xx Dad bought new, 1954WD45 PS, 1960 D17 NF

Posted By: clovis
Date Posted: 08 Sep 2010 at 3:52pm

I have a high quality Fairbanks Morse instruction manual for the FM-J mags, 4 pages, nice...9.50 shipped first class.

Posted By: Ole Shovel
Date Posted: 08 Sep 2010 at 9:46pm

That's what I was guessing too but never seen original parts manual for older B to know for sure. This guys B has a Wico C on it and I told him it probably had the FM J4B3 orginally but who knows for sure. The FM J came out about 38 or so and other brands 34 to 37 used FM RV mags and a FM mag application chart I have just says FM RV or J or later FM X mags for B of all years no break down of when changes were made by serial number or anything so I was just wondering if you AC experts knew more than me. I don't need a mag manual I have all kinds of FM and other mag manuals scanned off will send to anymore free of charge because sooner or later they will need parts or a repair service is how I think about it.

Posted By: morton(pa)
Date Posted: 08 Sep 2010 at 11:04pm

I have only seen Fairbanks Morse mags on B's. All the ones I own have an FMJ4B3 with the exception of the one which has an FMX on my '52, which I am told is a rare mag and was used as a dealer replacement to the FMJ4B. Can anyone confirm this?

Posted By: GlenninPA
Date Posted: 09 Sep 2010 at 5:29am

The FMX are not rare, just not as common as the FMJ.

Posted By: JCSinPITTS,PA
Date Posted: 09 Sep 2010 at 8:42am

this whole mag thing is very interesting!! I printed out an earlier post about what the number mean and certain number mean AC and the different (newer) model numbers. Is there a definate idea on which mag is the best, like is the latest version the one with all the improvements or do people still go with an older model to be corrrect?

Posted By: Ole Shovel
Date Posted: 09 Sep 2010 at 9:39am

Like said the later small body FM X4B3 is not rare in 30+ years working on them seen lots of X4B3 on AC and Lincoln welders with Continentals. FM made a large body mag the XO & XOR that replaced the FM K that isn't seen often and it had improvements in it. The small body X replaced the J. They moved the dist gear from the cap in the J to the bearing bracket on the X, different points, different dist gear, the main housing and magnetic rotor are different part numbers between the J & X also. Improvements I wouldn't say any or much just that it's easier on the X to see how to align the marks on the dist gear. If the little nub is broke off the points on the X are a real pain to set or have to replace the bracket new. FM X & J coils are the same, condenser is same too with new ones being foreign made junk in my opinion. If his Wico C needs to much may fix him up with the FM J if that is what most came with original just first time anyone brought in a Wico off a AC so I wondered when he wanted original mag. The FM X was still being not sure now and the place in OKC did have new ones yet sold some 3 years ago for Lincoln welders but the new FM mags are too high compared to a new Wico XH. The 3 number in FM-J4B3 designates it fits Allis Chalmers. Here is a link that explains the FM numbers.

http://www.oldengine.org/members/diesel/Magnetos/MagFMType.htm

http://www.oldengine.org/members/diesel/Magnetos/PetrolMag.htm

Posted By: Dave Everett
Date Posted: 09 Sep 2010 at 12:43pm

my 1940 factory book shows fitment of a Fairbanks Morse FMO Magneto with a footnote page (1944) stating that FMJ is to be fitted on exhaustion of existing FMO stock.

Posted By: Ole Shovel
Date Posted: 09 Sep 2010 at 2:19pm

Thanks Dave that's interesting. The FM O is another large body FM mag like the K, FM4, H, OH, OR, XOR and Z mags.

Posted By: Steve in NJ
Date Posted: 10 Sep 2010 at 7:13am

As with any mfr. mass producing, AC had a backup mfr. for Mags as well, and Wico was the backup mfr. It wouldn't be hard pressed to see a Wico "X" series on an AC machine when it was new, especially if the F/M's got thin temporarily as production went along. Pretty much any of the model F/M's mentioned above will fit the B model with flange mount and a 30 degree lag. The "J" was the most popular as I mentioned in another post on this topic, and improvements were made along the way as models replaced models. The "X" series Mag is probably bout' the best performer in my opinion for a factory installed unit. More user friendly especially when working on the unit right on the Tractor...

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