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KW High Bar Magneto Problems

John Rhodes

We have a four cylinder KW High Bar Magneto on 25-50 Minneapolis. This weekend we were having issues in which the tractor would run for 20 to 30 minutes and then would start running on two cylinders then down to one and then quit. We have gas and the carburetor is working. I was told that the magneto condenser is the problem. I don't know much about magneto's so I was hoping to get some thoughts on if this might be the possible problem or if it could be something else.

Thanks for you help.


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While I can’t say this is the problem you have with the KW, we had a tractor once that would run fine when first started but after 30 to 45 minutes it would start missing. It would progressively get worse until it finally died. If we let it sit for 2 or 3 hours it would cool off, then fire up and run good for another 30 minutes or so till it repeated the whole thing. Knowing that it had to do with fire to the plugs, we pulled the mag and sent it for a rebuild. We put it back on and never had another problem with it.


Without testing the magneto you can only guess what the problem is. Two possibilities come to mind and the simplest is to replace the condensor and go again. The other is the coil getting hot and arcing out so that would mean another coil required. But these are only guesses and you need to have it tested to find out the exact problem. Sometimes you will diagnose it with a multimeter and other times, like this it will need to be tested when hot to find out what is failing.
If you would like the tractor to be a reliable one again send it off for a repair/rebuild.

Andrew Mackey

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Replacing the condenser iis the cheapest option. What you have to do to replace it is another issue. On some mags it is easy. On others, it requires a tear down that can get quite extensive. it all depends where the condenser is. if it is under the distribution cap, near the points, you probably can do it yourself. if it is in the armature, best let a mag guy fix it. With the hot weather lately, are you sure the tractor is not making a vapor lock? Are you sure spark is being lost? easiest way to tell is to buy some neon in line spark testers from an auto parts store. if the glow stops, you have a mag problem. If it stays steady, then I wold think a fuel issue (debris in lines or vapor lock from excessive heat to the fuel)


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I'm still trying to figure out why I cant remove the brushholder (I think) from mine. Part number 183.

Its a Model HK and looks like a beauty but I've never turned it and won't until I can disassemble it for cleaning and the stuck brush gizmo is holding up the show.

Here is some reading material:

The same site has more, too.


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On an HK magneto changing the condenser requires complete disassembly. The condenser is in the center of the mag under the magnets, and is the old style of paper and foil about an inch and a half square.