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Different starter on SJ- Anyone rebuild?

Discussion in 'The Garage' started by BBS360, Mar 14, 2017.

  1. BBS360

    BBS360 XS400 Guru

    The starter motor on my XS400SJ doesn't seem to work.
    Tried jumping it right off the battery. No rotation, lots of sparks.

    Took it apart last night. Doesn't actually look too bad inside but it's different from the usual XS400 starters.
    No field coil. Permanent magnets.
    Four brushes.
    Looks like this might be the right kit:

    Wondering if anyone has had issues with these starters or rebuilt one?
  2. xschris

    xschris miles of smiles =)

    http://www.ebay.com/itm/YAMAHA-N-O-...ash=item53f4327e8a:g:osYAAMXQgfZRCF5g&vxp=mtr Looks like they made the brush assembly as a one piece replaceable part rather than all the bits separate for just this model. After looking at the parts diagram it looks still like the same unit. My 82sj has the same unit as all my other e-start bikes. I even put a 76 xs360 starter in my 80sg. As for rebuilding one most any shop that rebuilds car starters or alternators should be able to do this for cheap.
  3. BBS360

    BBS360 XS400 Guru

    Externally it looks identical except there are no screws in the middle (field coil mounts?).
    Gave mine a very thorough cleaning with acetone, filed off a burr on the commutator, cleaned between commutator segments(no mica between), reassembled with extra care to get the alignment right.

    Jumped it off an alarm battery that's really not meant for the high current draw... got sparks but it twisted in my hand.
    I think it'll work.

    Photos if anyone is curious.
    20170314_192422 (Medium).jpg 20170314_191815 (Medium).jpg 20170314_192010 (Medium).jpg

    Thanks for the ebay link. Brushes are still about 12mm each so there's lots of life left.
  4. BBS360

    BBS360 XS400 Guru

    After the previous cleaning and reassembly the starter did work for a while. Used it on and off over the summer while wrenching on the bike. Did get the bike running with it.

    Then it stopped. Went back to the same behavior. Starter would click and... Nothing.
    New clue though is that it's actually tripping the overload circuitry in my lithium battery. Battery shuts down for a few minutes after each attempt.

    Seems like it's shorted internally or the shaft is locked, but the shaft isn't locked.

    Took it apart again last night. Noticed this time that the magnets are actually cracked. They are still very securely epoxied in place and it looks like they were cracked in my previous photos, so I'm not sure that's actually the problem. Might have reduced output but should still work.

    The stock armature resistance is too low for any regular meters to differentiate from a dead short, so there's not much to diagnose without specialty equipment.
    The magnets are not replaceable and actual damage to the bike seems unlikely so I'll try again.

    I've done another thorough cleaning, removing buildup in the gaps between commutator segments and dressing the commutator (as per a post by Pamcopete on another forum.).
    Will try it again when it's slightly warmer out.
    I did determine that it's a Mitsuba SM-8205 starter motor.

    Attached Files:

  5. BBS360

    BBS360 XS400 Guru

    Thinned some JB weld to get into the cracks and reinforced the existing epoxy with more JB weld.
    Works when jumping it straight off a battery.
    Will reinstall sometime in the next couple weeks.
    Still cold outside.

    Out of curiosity I measured the peak current which came out to 46.7A or .58kW @12.5V.

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