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Bad stator?

Discussion in 'XJ Technical Chat' started by parts, Mar 28, 2011.

  1. parts

    parts Member

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    Just put in new alt harness and brushes but not getting more then 11.98 vdc at the batt.
    The original harness had come in contact with the rotor and shorted, thus
    the backfiring and engine stumble.

    some points;

    While waiting for Chacal' new harness to arrive I replaced the timing chain,adj valves, cleaned carbs, new plugs etc for the fresh new riding season to begin.
    Runs like a cheeta on fire untill the draw on the batt begins.

    Any ideas???

    thks,
    ron,
     
  2. parts

    parts Member

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    Come on guy's. Too many guru's not to know lol
     
  3. PainterD

    PainterD Active Member

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    It's either the stator or the voltage regulator if the wiring is good. Check all those plastic plugs also. They get corroded and heat up which can cause them to melt from a poor connection.
     
  4. waldo

    waldo Member

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    ohm out the rotor and stator wires. check grounds if you shorted the wires you might have fried the regulator
     
  5. Tomh

    Tomh New Member

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    If you know your battery and all connections are good, and checked the stator for shorts ground, the rotor ohms out okay, you can check the output of the alternator.
    With the bike running, check the stator output at the harness connector before it goes to the reg/rect. Put a volt meter on A/C volts and ground negative test lead and check each of the yellow wires individually (the ones coming from the stator cover). If my memory is right, you should see about 30 volts (AC!) coming from each stator lead. The main thing is they should all read the same (or very close to it). With thin test leads you can check the backside of the connectors without unplugging it. If you are getting good even A/C voltage across all leads, the rotor and stator are fine. Look at the rectifier/regulator next. There is a way to test the rectifier thats pretty simple but I don't remember how to check the regulator but if the alternator is working and you're not getting voltage from the regulator its probably shot.
    Hope this helps some.
     
  6. parts

    parts Member

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    Thanks all.

    TomH you were on the right track thanks!

    The meter said 0 vac @ the stator plug (@ reg/rec).
    I checked it plugged and unplugged.

    If the stator is fried can I still get a good read from the rotor?
    I beleive it should read 4.0 ohms.

    Also;

    batt vdc 12.29

    Brush harness (brand new ( thanks Len!) @ rec/reg 15.0 +- .3
    This should only read 4.1 +-10%

    reg/rec show's continuity but only for a brief sec then meter go's
    blank. Is that normal or just a fluke? The manual gives no values
    when checking the reg/rec , only O X.

    I'm going to check the rotor ohms next.
     
  7. parts

    parts Member

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    Rotor field coil resistence reads 5.0 to 5.2 all the way around.
    should be 4.0 +- 10%.

    alt plug @ loom reads 0.01/0.00 which if I remember is 0.46 +/- 10,
    However the manual states this value should be minimal. I take that
    to mean I'm ok.

    So,charged batt, new brushes and harness set, stator reading good at the harness but, 0.00 vac at the reg/rec plug (bike running), and above norm reading on the field coil I guess I need both stator and rotor.

    Any other tests you guy's can think of before I start on ebay would be
    great.

    thx
    ron
     
  8. bigfitz52

    bigfitz52 Well-Known Member Premium Member

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    I highly doubt you need both stator and rotor.

    Have you run through the charging circuit diagnostics in the factory book?
     
  9. parts

    parts Member

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    T
    I agree and question my own findings.

    So.... the manual only gives me an x and 0 for the reg/rec meening open
    or closed. My meter agreeds with this.

    From the brushes (again brand new from Chacal) to the connector read 15.0 ohms. should be 4.0 ohms.

    From the stator to the connector reads 0.00 vac when the bike is running. Idle to 3k. Should be 30 vac.

    With the bike off, the stator connector reads 1.46 ohms, but should read 0.46 +/- 10%.

    The rotor's field coil reads 5.0 to 5.2 ohms depending on meter location. Should be 4.0 ohms +/- 10%.

    So if unless 5.1 ohms is acceptible then both mst be out.

    I found a short in the brush harness (red/grn leads) thats why I have the new set from Chacal.
     
  10. David3aces

    David3aces Member

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    With the alt assembled, take a .001 or .002 feeler guage and hold it 1/8 inch from the alt. cover and turn on the key. Does the magnetism pull the guage to the cover? If not, it's the signal fuse, rotor, brushes, or regulator. The rotor becomes an electro magnet when the key is on and either the regulator regulates by adding or removing the ground to the field coil (rotor) or it regulates the power leading to the field coil (rotor) I forget. You can apply 12 volts directly to the rotor with the brush wires to see if the rotor becomes a magnet. If the rotor works by applying power to it and doesn't with the regulator connected then it's bad.
    Make sense? Old yamaha trick.
    You also want to check AC output between the stator wires themselves. Not between the wires and ground.
     
  11. parts

    parts Member

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    Yes I think I get what your saying.

    I did meter the stator leads at their plug and got a big fat 0.00 ohms.
     
  12. parts

    parts Member

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    Ok thanks guy's.

    I know it's unlikely to lose both stator and rotor but remember;
    There was a short in the brush harness that came in contact with
    the rotor while under load.

    The rotor (after polishing it's surface) is 5.9 ohms. Thats 1.60 ohms
    above tolerence.

    The stator is not showing any life at all.
     
  13. 82secacustom

    82secacustom Member

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    Hi there I had the same problem last year with my bike. Have you checked the wire where it connects to the stator? It is quite common for the wire to get crushed between the engine and alt cover and lose connection and stop working. That is what happened to mine, I actually took the two ends and heat shrunk them together until I got a replacement which worked lol.
     
  14. parts

    parts Member

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    Yes, after all the testing was done I sliced away the sheath and found a very
    small spot that got pinched but not cut. just a little wear to the insulation.
    Unfortunatly, even e-taping the bad spot did not help-still getting 0 vac
    and around 1.6 ohms.
    After a thorough cleaning the rotor is still reading 4.9 - 5.1 ohms.

    Looks like I need both.
     
  15. 82secacustom

    82secacustom Member

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    How do the connection leads look you said you shorted out at one point could there be any sort of moisture in the lead and now the lead is useless? Any sort of build up on the lead?
     
  16. parts

    parts Member

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    Thanks 82secacustom, No moisture because one of my twice a year (analy retentive to be sure lol) maint S.O.P.'s is to clean the elec connections and apply die-electric grease.
    But this is now all a mute point since I've chosen to replace the entire charging system. (thanks to Len for having all the goodies in stock).
    stator
    rotor
    rec/reg
    brushes, brush back plate and harness.
    batt
    So it should be flying down the road in a few day's.

    As this will be the first rotor I've replaced any advice or "dont do this"
    would be great.

    Thanks guy's!!
     

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