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Farmall & IHC Tractors Discussion Forum
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McCormick Magneto question

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bigr

11-05-2007 13:23:27




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What is the proper way to test a mag off the the tractor for spark? I sent my mag for my 10/20 to a vendor to be rebuilt, he had it 2 months sent it back and it had no spark, sent it back to him and haven't heard from him since. Before that I sent 2 mags to him and he was great. It's been 2 months again and can't get ahold of him. Not sure what to do. So I got a mag from a buddy of mine off of a F20 and before I try cranking the tractor I'd like to know I have something to start from. Any help would be appreciated.

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LenNH

11-06-2007 07:10:51




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 Re: McCormick Magneto question in reply to bigr, 11-05-2007 13:23:27  
The impulse-coupling alone should give you a hot enough spark to see if the mag is working. If you have something that will grip the drive, you should be able to make it click over enough to see if there is a spark. The impulse was designed to make up for the very weak spark that would be produced at hand-cranking speed. Early airplanes, and some cars (Model T Ford, for example) did not have impulse couplings, and there were a couple of ways to provide the spark needed for hand cranking. Some airplanes had an
auxiliary generator that the pilot spun to give enough spark while a mechanic turned the prop. The Ford T in its later life had a battery that could be turned on for starting current. The very weak spark made by hand-cranking was one reason people resorted to trying to spin the crank, to get a hotter spark. Problem was, sometimes the engine got cantankerous, like a mule, and kicked. The result was a broken arm. Happened to my father back in the 20s when he tried to spin a Ford T.

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russ hamm

11-05-2007 16:11:03




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 Re: McCormick Magneto question in reply to bigr, 11-05-2007 13:23:27  
I put two bolts in the base and clamp them in the vise. I built a tool that fits the impulse coupler to turn it, but used to use a vise grip on the tangs of the coupler. This way you can check the impulse.



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F-Dean

11-05-2007 13:42:12




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 Re: McCormick Magneto question in reply to bigr, 11-05-2007 13:23:27  
This is how I bench test a mag. I learned most of it from this site.
1. Get a 3/8 drive socket to fit the nut on the drive end of the mag.
2. Cut a 3/8 drive extension in half.
3. Put the half of the extension with the male end into your electric drill.
4. Put the socket on the end of the extension.
5. Put a spark plug wire into the mag and place the other end close to the frame of the mag. DO NOT hold it in your bare hand!!!
6. Use the drill and socket to rotate the mag the proper direction.
7. A good F-4 mag will produce at least a 3/8 inch spark

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