John Deere 'D' Magneto

ROSchell

Member
I'm wondering if anyone has any experience with the magnetos on the John Deere D. My D is a 1938 Model with the Edison-Splitdorf Model CD Magneto. My dad re-built this tractor in the mid-1980's, but never got the paint finished. We could never start it by the flywheel, but would have to move it once a year to get access to our crop sprayer, and we would pull it about 10 feet and it would pop right off. At that time, we had an old John Deere mechanic as a neighbor, so I'm thinking him and my dad went through the magneto and got it timed and such. Anyway, both have since passed away, my dad being gone for 8 years now.

Well, I remember the last few years we would start it, it started spitting and backfiring, and it seemed that each year it would be worse. After dad died, I continued to start it and it ran for maybe the first two years after he passed away, while the coughing and backfiring still got worse each time. Finally the last time it ran, it quit completely and would no longer start at all. I saw that the gas tank was all full of crud, so I thought maybe that was the problem. I took it off a couple of years ago, cleaned it out, and lined it with Red Coat. I also put a carb kit in and yesterday pulled it out for the first time after getting it back together, but no luck. It wouldn't fire at all. After a few trips of being pulled around the block to try and pull-start it, I took one of the plugs out and routed the wire back to me and there was no spark at all on the plug.

I just talked to Albert and Renaissance Tractors regarding a gasket for another of my tractors, and I mentioned this to him and he suggested switching magnetos to a Wico Model X. He says they are much simpler and produce hotter spark. I am wondering if anyone has ever done this, or if there are any other suggestions. As far as keeping original parts, I guess I just want the tractor running again in memory of my dad. Thanks for any opinions or advice and sorry this got so long winded.

Randy
 
It sounds like the original problem was the impulse in the mag was not working. When you hand start an old JD, the RPMs are not high enough to produce a good spark from the magneto. To compensate for this, a spring loaded device called an impulse winds up and trips at the point where spark is needed. The wound up spring spins the mag at a higher RPM temporarily to produce the speed to create a proper spark. By pull starting it you are spinning the mag fast enough that the impulse is not needed. When you roll the tractor over by hand you should hear a plainly audible click twice each revolution of the flywheel, if not, your impulse is not working.

Now that the tractor has sat for some time, the internal parts of the mag, such as the points and condenser, may need some attention as well. You may need to go through the fuel system again as well if you did not drain it dry.
 
I had the same issue with my 1939 D. I had the original Splitdorf mag rebuilt 8 years ago. The impulse spring is weak, and would no longer start by hand. Pull 2 feet and it will start. I could not find a new spring, only used ones that were as old as the one I had. I went with a rebuilt Wico X. What a difference. That mag fires every turn. The tractor starts much faster. Most times with out the choke. The parts are easier to find, and it is easier to service. Good luck with yours!
 
Thanks for the replies. Sounds like maybe I should upgrade to the Wico X Magneto. From what I've been able to find, it should be a long lug, correct? Is there a more specific model number of the magneto that I would need? I would probably buy it from Renaissance Tractor as he was very helpful on the phone this morning. I may have found someone who would be willing to look at the Edison-Splitdorf, but according to the comments, the Wico would provide a hotter spark for the old 'D', so unless it's something simple like points and condenser, I will probably go with the Wico. Thanks.
 
I have been running a Wico X magneto on my 1947 D since 1989. No problems, starts very reliably, idles very good. I have listened to D's running on Edison-Splitdorf mags and I think they will allow a bit slower idle without the impulse clicking, but that's not important on a working tractor. You do need a long lug magneto.
 

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