Johnson LT 10 Magneto HT Brushes

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  • July 30, 2016 at 9:26 pm #4879
    sputnik16335
    Participant

      Good Afternoon, All

      I picked up a ‘barn fresh’ Johnson LT 10 serial #346538, cosmetically fairly nice, but the pistons were stuck. I got it freed up, and discovered that it has no spark. I pulled the flywheel and found that the high tension brushes have been monkeyed with, and were pretty bent up. I’ve got them pretty well straightened out, but I think they’ll need more tweaking.

      I’m going to look for replacements, but meanwhile, I’d like to tinker with the existing ones to see if I can get them working. The manual recommends a special tool to adjust them. Is there a way to do an acceptable job without it? The pictures seem to show the brushes to be straight except for a short turn up at the end. I assume they should be flat against the flywheel contact. Any other suggestions for tweaking the brushes or the mag in general?

      Are replacement brushes available?

      Thanks,
      Rich R.

      July 31, 2016 at 12:47 am #41265
      garry-in-michigan
      Participant

        Lifetime Member

        Hard contact is not necessary, it only results in excessive ware. They should however make good contact the flywheel. The flywheel must be clean, dry and smooth. Two flats on the cam enable the points to fire every half revolution. The "Brushes" short out the non-firing spark plug wire acting as a distributer. All insolation must be clean and dry. While the flywheel is off, check the spark plug wires for shorts to ground. Like any distributer, they can develop carbon tracks to ground. They are hard to spot and look like cracks. They may have a high resistance, but are still less than that of the spark plug and will be a disaster for ignition.
        Good Luck . . .         . 🙂

        July 31, 2016 at 4:06 am #41279
        hotrod
        Participant

          You could measure the diameter of the bakelite hub/grounding brass in the flywheel, where the 2 brushes should contact. Then the brushes should be centered and a bit closer together than that hub diameter measurement. They are generally straight out.

          July 31, 2016 at 2:31 pm #41299
          sputnik16335
          Participant

            Thanks for the info, and the explanation. Sounds easier than I thought. I hope I can get them straight enough to make good contact.
            Cheers.
            Rich R

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