Farm Equipment - 1941 Allis B timing problems

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1941 Allis B timing problems

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=137094
Printed Date: 08 Nov 2025 at 1:49pm
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Topic: 1941 Allis B timing problems

Posted By: Revilo
Subject: 1941 Allis B timing problems
Date Posted: 06 Apr 2017 at 12:43pm

Hello from England!

I've recently bought a 1941 Allis B.
The guy I bought it from told me he'd never had it running. He also said it had a replacement mag fitted. When I got it home I found the mag to be in poor shape so I fitted a new coil and condensor.

I'm happy there's a spark but I'm confused as to how to time it.
The mag itself - Fairbanks Morse K4B.
There's a fibre gear that's confusing. It has an A (which I understand is anticlockwise) and a C which I've timed it to (which is clockwise).
On the pictures I've seen of these gears the A and C are fairly close together. Mine aren't, they're about 9am and 2pm, which worries me as to the mags suitability for this engine.

I'd appreciate some advice.

Regards,
Andy

Replies:

Posted By: steve(ill)
Date Posted: 06 Apr 2017 at 10:25pm

most of the mags I have seen have the A and C maybe 20-30 degrees apart on the gear.. I don't know much about YOUR specific mag.. that might be the difference. If you have the gears lined up as expected, you will get a spark........ if the timing internal is off, it will not spark....... since yours sparks I would assume it is OK and install on the tractor and rotate the motor by hand and see that you "spark" at the TDC mark on the crank ( top dead center)... the mag should go to advance ( fire mark) as RPM increases.

im thinking the FMK was an older design used on the WC tractors ?? 1930s ?

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Like them all, but love the "B"s.

Posted By: steve(ill)
Date Posted: 06 Apr 2017 at 10:28pm

http://www.oldengine.org/members/diesel/FairbanksMag/PetrolMag.htm" rel="nofollow - http://www.oldengine.org/members/diesel/FairbanksMag/PetrolMag.htm

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Like them all, but love the "B"s.

Posted By: Revilo
Date Posted: 07 Apr 2017 at 2:15am

OK, thanks. It'll be Monday before I get chance to have a go at sorting it. Cheers.