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Charging problem no charge at idle. Charge above that

Discussion in 'XJ Technical Chat' started by bomber737, May 10, 2015.

  1. bomber737

    bomber737 Member

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    I was servicing my girlfriend's 83 xj750 Maxim. I have a voltmeter wired in so I can keep an eye on the charging system. I just put a new agm battery in it that was fully charged. When instated the bike I noticed it was only putting out 11.5 volts so I know it was running on the battery. When I revved the bike up it started charging. I took it out for a ride and the voltage held steady at 14.2 volts. Once back at idle it went back to 11.5 again. I took the alternator cover and checked the brushes and they look good. Both are the same length. I also cleaned up the donuts for with some scotchbright. I reinstalled the cover and fired it back up and still discharging at idle. Anyone have any thoughts?. New voltage regulator?
     
    bomber737, May 10, 2015
    #1
  2. k-moe

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

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    What you are seeing is normal. The alternator does not spin fast enough to deliver 14.2 volts until you reach 2,000 RPM.
     
    k-moe, May 10, 2015
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  3. bomber737

    bomber737 Member

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    Ok Ill check it out. I had to unhook the tach as it was causing me electrical issues and blowing the main fuse. I took it out of the system and no more fuse problem. I just seem to remember that it did charge when it was at idle. I think is was like 13.1 volts. I guess well see wht happens with some more riding.
     
    bomber737, May 11, 2015
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  4. XJ550H

    XJ550H Well-Known Member Premium Member

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    no there is no charge going on at idle your running off the battery, I checked mine the other day.same results as what you are stating.
     
    XJ550H, May 11, 2015
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  5. bomber737

    bomber737 Member

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    Great, I guess she will have to have her limit her warm up time so she doesnt run her battery down.
     
    bomber737, May 11, 2015
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  6. XJ550H

    XJ550H Well-Known Member Premium Member

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    how long does she need to warm it up? could start riding with Partial " choke" once your moving shut it off
     
    XJ550H, May 11, 2015
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  7. bomber737

    bomber737 Member

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    Probably 5 minutes while she puts on her helmet and her golves. Maby a few min longer when its cold out. The bike is off choke in about 3 minutes. I colortuned the idle mixture screws and I usually check (adjust) the sync every spring so I know they are set up for the summer riding season.
     
    bomber737, May 11, 2015
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  8. Polock

    Polock Well-Known Member

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    just because their not charging the battery doesn't mean that they run off the battery. the bike is still making juice, just not enough to charge the battery.
    it can idle and not charge the battery till the engine overheats. Be more concerned with over heating
     
    Polock, May 11, 2015
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  9. hogfiddles

    hogfiddles XJ-Wizard, Host-Central NY Carb Clinic Moderator Premium Member

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    ....and unless its really hot out, you're not gonna overheat anyway. Besides, you're gonna be RIDING the bike----fast. You're not gonna spend all your time sitting on the bike at idle.

    Dave
     
    hogfiddles, May 11, 2015
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