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Lost spark

Discussion in 'XJ Technical Chat' started by Carey, Aug 9, 2017.

  1. Carey

    Carey New Member

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    1986 XJ700; has been chopped, been rewired by someone else, had it running great after carb rebuild for an afternoon but then lost all spark. Ign coils; 12v, pickups 118ohms, checked my grounds, I'm getting about 4 - 5 v from igniters during ign turnover. Could it be my igniters?
     
  2. k-moe

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

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    What condition is the battery in?
    Reply back with the battery voltage at rest, and what the voltage drops to when you thumb the starter.
     
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  3. Carey

    Carey New Member

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    New Lithium 12v 18amp 270cca;
    13.08 v rest 11.86v when thumb start.
     
  4. MattiThundrrr

    MattiThundrrr Not a guru

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    I don't think the battery will power the starter with less than 12 volts. That may be the problem.
     
  5. XJ550H

    XJ550H Well-Known Member Premium Member

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    9.8 -10 volts is the no start point
     
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  6. Carey

    Carey New Member

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    Ok.... the igniters have already been swapped out once & I had spark until the bike was ridden for a cpl hrs (around the block, what not). It was running great & then died, the battery was @ 10.97v when lost spark, recharged battery to full 13.47v, still no spark. I thought it was a bad ground but can't narrow it down. Now thinking it may be the igniters again???
     
    Last edited: Aug 14, 2017
  7. XJ550H

    XJ550H Well-Known Member Premium Member

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    you need to repete voltage drop test first.

    attach meter to battery take reading
    press starter button what does the battery voltage drop to?
     
    Last edited: Aug 14, 2017
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  8. XJ550H

    XJ550H Well-Known Member Premium Member

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    which xj700 do you have ? aircooled or watercooled

    also time to ohm out full ignition system.
    ignition coils primary and secondary
    pick up coils
    spark plug caps
    spark plugs.

    could be as simple as triming 1/4 inch off the end of the spark plug wires.
     
  9. Carey

    Carey New Member

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    My XJ700 is aircooled, I'll do a repeat of the voltage drop & double check the ohms. I did trim a litte off the plug wires alrdy but again cant hurt to repeat that. Thanks so much
     
  10. XJ550H

    XJ550H Well-Known Member Premium Member

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    on tci there is a black/white wire find the connector (not plug) and disconnect it. it grounds out tci killing spark

    specs
    XJ700 air-cooled models
    :
    Pick-up coils:
    120 ohms +/- 20% = 96 ohms to 144 ohms acceptable range
    Ignition Coils:
    Primary side (input from main wiring harness):
    2.7 ohms +/- 10% = 2.43 ohms - 2.97 ohms acceptable range

    Secondary side (spark plug wires, without their end caps):
    12K ohms +/- 20% = 9,600 ohms - 14,400 ohms acceptable range

    Spark plug caps:
    1986 S/SC models: 10K +/- 20% = 8,000 to 12,000 ohms per cap acceptable range


    Spark plugs
    :
    1986 S/SC models: 5K ohms per plug
     
    Last edited: Aug 15, 2017
  11. Carey

    Carey New Member

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    Hey guys, thanks for the all the help & XJ550H, you were right, in the process of re checking my ohm readings, I clipped my wires a bit & replaced my caps. Got spark now, sometimes you overlook the simple things...Thanks again..
     
  12. Carey

    Carey New Member

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    I spoke to soon, had spark after clipping wires & changing out caps then no spark. Re checked ohms; ign/pickup coils, caps, all good. Have 12.8 v to ign coils from switch. Wtf????
     
  13. Carey

    Carey New Member

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    XJ550h, in reference to your previous reply, re: disconnecting black/white off tci... can I simply cut that wire coming off the connector ?
     
  14. XJ550H

    XJ550H Well-Known Member Premium Member

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    if you push a sewing needle in to the connector from the front on the side of the contact with the tab that locks it into the connector body the contact will just slide out of the connector body. better than cutting the wire
     

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