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Plug Caps

Discussion in 'XJ Technical Chat' started by cds1984, Sep 5, 2020.

  1. cds1984

    cds1984 Active Member

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    Okay.
    Shoot me for this if I'm out of line but...
    I've been trying to troubleshoot a LONG standing issue I've had with my ignition and ended up at the coils.
    One was reading 30~Kohms and the other 200~Kohms.

    After removing the plugcaps and testing at the leads they were both good (coils I mean).
    so... down the rabbit hole.

    First I unscrewed and checked the resistors.
    On the bad coil they were loose and one resistor was just black and even after a cleanup, my multimeter couldn't read it.
    The other was okay (10Kohms) but after refitting it to the plug cap... nada! open circuit!
    What the hell!
    So... I have a HEAP of (5 or so) bikes worth of old coils and after testing and then disassembling the plug caps I ran into the same thing... OPEN CIRCUIT or close too.

    So...
    I smashed one of the plug caps apart to see how it was actually connected to the lead.
    A simple screw press fitted to a copper plate.

    Aha!
    So after much digression and trying to work out how to clean up the plate at the bottom of the plug cap I eventually ground the end of a drill bit, as in the the end that goes in the chuck normally, randomly and span that sucker in each plug top to clean out the gunge/carbon/etc, before replacing the spring and resistor.

    Now, instead of going insane I can actually see a reading on my multimeter when I test the plug caps.

    Not sure if this will help anyone but... I'm posting because I hope it might help.

    Oh BTW,
    I have BPR8ES (5Kohms) with plugcaps with 5K0hms now.

    That guy at cullys yamaha who said the resistors in spark plugs didn't mean shit can suck my... something or other...
     
    Last edited: Sep 5, 2020
    cds1984, Sep 5, 2020
    #1
    XJ550H and Rusty81 like this.
  2. Toomanybikes

    Toomanybikes Well-Known Member

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    New plug caps are cheap and more common a failure item than coils.
     

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    Toomanybikes, Sep 5, 2020
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    cgutz likes this.
  3. cds1984

    cds1984 Active Member

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    +1

    Troubleshooting on the fly calls for desperate measures in the meantime.
     
    cds1984, Sep 6, 2020
    #3
  4. Marchy

    Marchy Member

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    So I had a cap come off like it was nothin do I replace ?
     
    Marchy, Nov 15, 2020
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  5. Yammaat

    Yammaat Active Member

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    Had similar problems with my bike, the Secarat, and took me about 2 years to finally finding the culprit. But now, also after a new ignition and coils...;
    runs with removed capresistors. The resistorspace is now filled with very thin coppersilver wire from my loudspeakercable..lol
    Sparkplugs are the non-R type.
    Bike runs like a dream.
     
    Yammaat, Nov 15, 2020
    #5

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