undercutting Jinma 254 starter

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    • November 4, 2015 at 7:09 pm #45603
      donaldl
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        Gentlemen;There is no consensus on undercutting the commutator of a starter motor.Some say yes while others say no need.
        My starter motor on my Jinma 254 three cylinder tractor failed.The segments between the commutator bars were noexistant (not just clogged with carbon but gone).I rigged up my Foredom cutter and made a jig to hold the hand piece and cutting disc.Then mounted it perpendicular to my lathe,and regrooved those segments.Reassembled the starter and it works !!.Is this just temporary success,as the grooves quickly fill/erode the segmented grooves again?

      • November 5, 2015 at 10:30 am #45604
        Bob Rooks
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          The mica undercutting is good as long as it isn’t too deep. If the brushes are too soft the undercut will fill and cause arcing over on the com. Make sure the brushes are profiled correctly to the com.

          Account deleted.

        • November 17, 2015 at 5:52 pm #45660
          donaldl
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            Mr.Rooks;Thought I had subscribed to all posts but no alerts to your reply were in my email.I have about 30 starts on my regrooved/undercut starter.And I did not take extra care with the original brushes on commutator profile matching. So far,so good.Don L.

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