Fairbanks Morse Battery Ignition Unit B4B3

Allis 1941

New User
This item looks like a magneto, but no impluse coupler and needs a battery to then operate like a distributor. Does any one have an instruction sheet on it ? Did the Allis factory use it on new tractors ? When ? Is there a demand for these ?
Sound like you have a mag that someone has converted to battery igniton. I have NEVER seen one factory but seen a lot that were converted. Are you sure the impulse is not stuck as you need the impulse to retard the timing for starting.

Thanks for the reply. FM called these items BATTERY IGNITION UNITS. They look very much like a FMX magneto. No one has done any changes to my unit. I too have seen those converted to use an auto coil mounted on the engine with a hole drilled in the side for the coil wire and of course the old coil removed. Hopefully there is some one out there that has an instruction sheet that explains the hook-up. I think these may have been an alterative to using a distributor.
Could you post a picture. I work at an Allis dealer in the late 60's/ early 70's and I never saw anything like this inthe Allis parts books they had. If it has an internal coil I would suspect you would connect most likely 6 volt negative to the wiring terminal and time the unit to the engine and go.

small photo and comment at bottom left of this page

I have an FM-B4B3 that is new in the box, complete with wire and switch. I am planning to use it on a '48 B that I bought this summer. These are indeed a distributer with an internally mounted coil that makes them look like a magneto. They have a funny looking ballast resistor mounted on the outside, and instead of an impulse coupling, they use an internal centrifugal advance that can be adjusted through a hole in the bottom of the case. They are similar to the WICO model XB series that JD used for a short while. I'm not sure as to how desirable they are, given that parts are not likely to be as common as for the Delco distributers, but I think they're kind of neat.
Thanks for your response. That is indeed what I have in used condition. Does your new item have any instrucions or diagram on how to install ?? I need a copy if possible. I did find out that Allis installed these units on B engine SR#43946 thru 46895. And installed them on B model tractors during 1940. They are rare, why FM didn't keep making those is unknown.
No, there are no instructions with my F-M distributer. I have seen a couple of used ones sold on ebay, but they are certainly not as common as the WICO XB distributers.
I think I know Why these unit WERE NOT built very long. I think the main reason was WWII. A battery type igniton requires more material than a Magneto system. The battery system needs a battery, a generator, and a cut-out or voltage regulator. With the magneto you have everything in one package which used LESS strategic material than a battery system. The mag used less copper, steel, and little if any lead. By the time the war was over farmers who in this era were a VERY conservitive bunch, some still are, that a change to a battery ignition system would not fly.
A little story from my day at the Allis dealer. One day we had a Farmer in the shop who was having magneto problems with his tractor. Mind you this was in the late 60's or early 70's and cars and truck had been using the Kettering point system of ignition, what we call Battery ignition for about 40 to 45 years. The vehical this farmer drove to town had a battery igniton. Our mechanic was working on his mag and was having some trouble finding the problem. He ask about a new ignition system for his tractor. I tried to sell him one of the battery convertion that was available then from Allis. I think at the time they were around $50. He would not hear of it. He wanted a new magneto. I looked up the part number for the mag. Yes, we could order one for about $400. He did not order the new mag and he did not buy the battery convertion as the problem was found with his old mag.

If it has a wire going to it that has voltage it is not a mag.
The one like in this forum needs power from the battery.
Any wire going to a mag would be a ground wire from a switch to kill it.

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