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Alternator Question

Discussion in 'XJ Technical Chat' started by zemville, Jul 18, 2023.

  1. zemville

    zemville Member

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    Hi all,

    I've been reviving the old 1982 XJ650J which has been sitting for a quite a long time. I have already sorted issues and right now, I am at checking the charging system and found out that I only get at max of 13.7-13.8volts max past at 2k rpm. I have already tried changing the voltage regulator/rectifier unit as I have a spare but still yielded same results.

    I have tested the stator and rotor with what is specified on previous posts here same as the Hayne's Manual and found both STATOR and ROTOR to be off spec. The stator reads at around 0.6-0.7 ohms each phases whilst the rotor reads at 6 ohms. I can still see the line on the carbon brushes.

    Is there a way to renew/clean the windings to sort out the problem and hopefully get the correct output voltage for the bike?

    TIA - cheers!
     
    zemville, Jul 18, 2023
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  2. Mezzmo

    Mezzmo Active Member

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    Sounds like the rotor needs to be cleaned and maybe you need new brushes as well…
     
    Mezzmo, Jul 18, 2023
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  3. zemville

    zemville Member

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    Hi Mezzmo,

    How do we clean the rotor? I can still see the line in the brushes and it still have a plenty left to it.

    Thanks
     
    zemville, Jul 18, 2023
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  4. Rooster53

    Rooster53 Well-Known Member Premium Member

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    Battery condition is a big part of that and per the FSM the 14.5 +/-.3V is with a fully charged battery. So before calling it bad the battery needs to be fully charged
     
    Rooster53, Jul 18, 2023
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  5. zemville

    zemville Member

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    Hello, I do have a fully charged battery.

    I do think I need to clean the rotors if possible or maybe clean the brushes end as I have not done it ever since I got the bike.

    Cheers!
     
    zemville, Jul 18, 2023
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  6. Mezzmo

    Mezzmo Active Member

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    Hi mate, just clean the rotor with some "wet and dry", I'd use around 600 or even 400 grit. It should clean up easily...

    Then you may as well install new brushes and you should be sorted..
     
    Mezzmo, Jul 21, 2023
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  7. k-moe

    k-moe Pie, Bacon, Bourbon. Moderator Premium Member

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    Use a hard art eraser. Any grit paper will embed some of the grit into the copper, and cause the brushes to wear faster. Crocus cloth works too if you have it.
     
    k-moe, Jul 23, 2023
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