Magneto coil and heat?

JDEM

Well-known Member
I ran y little Oliver HG dozer all week in the Michigan UP. Took out a lot of huge stumps and built some more road. Kind of amazing little machine. I will not though that the soil here is all sand and that made grubbing out big stumps a lot easier. This crawler has a lot more traction then power. I have a aux trans and if I ran it in the original lowest gear - the engine would stall when pushing on much of this stuff. I was in low-low with most.

I am still cursed with the hot-coil problem (as far as I can tell). I am on my 2nd magneto and third coil. I can run 3-4 hours steady before the magneto gets so hot, I loses spark. Once it cools, it runs good again. I assume theses things were tested when new and did not have the problem back in the day? Hard to figure. Only two new variables here I can think of. #1 is new aftermarket parts maybe not as durable as the original? #2 the exhaust manifold is closer to the magneto then it was when new. The original exhaust manifold on the Hercules engine swept up higher and had "Oliver" letters embossed on it. This has a Hercules replacement manifold that sits a lot lower. It came with a special Z-shaped carb adapter since the carb has to be mounted lower to make the manifold fit.

Funny things is - while in the woods, I came across this old IH on an adjacent 800 acres of hunting land. Looks like it was left there many years ago. To my surprise, I turned the crank and it is NOT stuck. Even still has compression. Has an IH distributor on it instead of a mag that just might fit my Hercules.
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That little I h (farmall A) has a magneto with the distributer cap attached to the mag.
It might be good to find an original manifold for the HG or at least a heat shield of some sort
good luck.
Kris
 
A simple tin heat shield tucked in between the manifold and mag might solve the problem. Jury rig a piece of tin in there and see what happens. If it solves the problem you know what works.
 
Just my incorrect assumption. Technically, it IS a distributor. Just not a battery-ignition distributor. I did not even look close until I got home and uploaded the photos and saw the unit is an IH. I thought maybe it was a Delco battery distributor like my Case DC had on it. The one on my Case had a right-angle drive and no way it would fit.

I guess I could just mount an external oil-filled battery coil somewhere and just hook it to my mag and make a battery distributor out of it. I don't have a shop to work in or many tools up there and would like to avoid any modification projects out in the woods.

That all said, I wish I had converted the crawler to a 12 volt system and stuck my Fairbanks Morse distributor on it before I moved it to the UP. Somewhere in my tractor-parts junk-pile I have a tang-drive, four-cylinder FM battery-distributor that has the same footprint as my mag. I might have to dig it up this winter (hopefully) and see if I can find a way to convert it to breakeress.
 
I have an oc3 also, it would run a while and then quit. Got to checking and found a small hole in the manifold that was letting the exhaust blow down on the mag. I got a new one from Steiner tractor and no problems since then.
 
Here's a picture of an IHC H4 "MAGNETO" (Like Teddy mentioned it was). It looks a lot like the unit on your machine, except shinier lol...

John T
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Just bought a Hercules IXB engine a couple weeks ago. It came out of a running OC3, and has an IH magneto just like the one on that A, and isn't l cobbled on there. Actually looks like it could have came with it. Our HG has the Wico like they're supposed to have. I have the correct manifold for that HG/OC3 if you need one.
 
I too go for the heat shield solution. Root problem is probably the copper. It has a pretty good temperature coefficient meaning it changes resistance readily with temperature. That's why, when you see things like a power distribution standard where they talk about a 2% drop for a ......sized wire at a ....... current, the temperature is specified.

Copper gets hot, too much resistance in the circuit, limits the current to the plugs and as a results not enough energy to jump the gap and stay lit long enough to explode the fuel.

Many many times I have seen people with similar time related problems and find it's to the coil getting too hot.
 

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