Allis WD Mag Overheating?

fixer2u

Member
Hey guys, we have an odd issue with our WD. When it gets above 80 degrees outside our WD does not run right. The radiator is full, the shudders are open, and it runs great during cooler weather. Once it gets heated up it starts popping and farting under load. Then will not restart with the electric starter. The only way to get it to start is to pull start it.

I have changed plugs and wires and polished the points, but it doesnt seem to make a difference. What else could it be? It has been painted. Id there a vent on the mag or something that could be painted over?

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That mag is most likely a Fairbanks Morse FMJ4B3. There are tiny vent holes on bottom of the cap housing next to the cap. The problem could be the condenser, the coil, or many times the magnets need recharged after 50+ years' service. It might be practical to replace the mag with a battery ignition system.
 
Never good to paint a mag since yes they have vent holes that need to be open it they can not breath and that causes both condensation problems and mags to heat up and cause other odd problems. So you need to get the vents open and even then by now the coil may have gotten hot enough to be bad. Send me an e-mail and I'll send you the manual for that mag. I have manuals for both the common mags used on the A/C tractors
 
Mag needs to be rebuilt. Same scenario we had with WC and C when growing up......crank all day and no start...pull it 5 feet and it runs!
 

Ours only does this if its hot outside..... Let it sit til it cools off in the evening and fires right up.... But I see your point, looking for parts now.
 
Followup Time.

I was able to get the Coil and Condenser for the Fairbanks Mag.

I put the parts in and it fired right up and ran pretty strong!

I thank you all for the input!

2 issues though.

1. I did not see the vent holes you all described. Does anyone have a pic of them so I can see exactly where they are? The pic in the manual is shotty at best.

2. I had a little trouble getting the timing right in the mag. The manual says to look for the "Marked Tooth" on the pinion gear to place between the 2 marked teeth on the distributor gear.

All of the teeth on the pinion gear seem to be the same.... I do not see any kind of marking. What should I be looking for? I know on our Farmall B the marked tooth has a slight taper on the front.
 
Thank you Stu. I did not see any beveled teeth, like in the last picture, but I will look for that dimple you are showing in the other 2 pics.
 

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