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Failed coils? Probably not, but...

Discussion in 'XJ Technical Chat' started by DoubleTigerLefty, May 9, 2017.

  1. DoubleTigerLefty

    DoubleTigerLefty Member

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    ...open resistance on both HT leads to the coils
    -chopped a bit of the insulation back on the HT leads, multimeter reads open. MMeter Functioning perfectly

    reading closed cuircuit directly between pickup coils
    BUT
    -zero readings between pickup wires at TCI
    - will do more thurough examination of wires (which run along the base of the bike, and disappear in between components


    ---HOWEVER---

    I do get sparks (albeit weak) when I pull them out and ground them to the engine case, and hit 'start'

    BATTERY is @ 12.51, will charge for tomorrow


    ^^disclaimer^^^

    1. PO's genius (aka my younger self's genius) makeshift "electrical pan" most likely held water during the winter. Stored outside and neglected while I was taken out of town on emergency. Long story, please resrve judgement

    2. Tank sealant was all over the plugs when I took them out, another side effect of the failed tank sealant which resulted in me having to shell out hard-earned cash for new carb bodies, new fuel tank, degreasers and chemicals and petcock. So new plugs will be bought anyways.

    3. Got rid of starter cirucit cutoff relay. Bike turns over fine, still doesn't fire.

    Please leave any comments you may have as to what this strange lack of resistance could be the result of (specifically; I understand it was out in the rain, unfortunately can't do anything about that except not repeat it.) and why i seem to have )weak( spark regardless of lack of resistance, and what the next thing you would do.

    I will report tomorrow with results of further quests through this month-long journey through my ignition system.

    Much love.
     
  2. Stumplifter

    Stumplifter Well-Known Member

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    The oozing tank sealant, sounds like The Blob.
    Was this an etching to adhere sealant? How bad do the rubber bits that were exposed to it look?
     
  3. XJ550H

    XJ550H Well-Known Member Premium Member

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    are you testing from spark plug lead to spark plug lead?
     
  4. Toomanybikes

    Toomanybikes Well-Known Member

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    I do have spare coils and such for your bike. saw that bike in the Pic on Craigslist about a year ago, always wondered who got it
    I'm out in Tsawwassen
     
  5. DoubleTigerLefty

    DoubleTigerLefty Member

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    Awesome to know, thanks, toomany. I put. A lot of love into her since, but this einter was a cataclysm for me and the bike, but she's just about perfect. Soon as i get sparks back to bright and blue...

    I was testing the same HT circuit, lead to lead. Open resistance, but it says in the manual to look elsewhere if such a problem arises... resistance is resistance, though, so i dunno... will report back asap
     
  6. Toomanybikes

    Toomanybikes Well-Known Member

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    Have you done this on muti meter?
    I have done it , oops and wonder why no readings
     

    Attached Files:

  7. DoubleTigerLefty

    DoubleTigerLefty Member

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    No, mine is simpler, with only two plugs. After work today, ill be doing a few tests which the mechanics at my work suggested.
     
  8. DoubleTigerLefty

    DoubleTigerLefty Member

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    Okay, so the tests returned the following results:

    Pickup coils @ tci are in spec.
    Secondary windings are 11.9 and 11.6 - This is WITHOUT the caps, multimeter shoved right up into the wiring.
    Primary windings are BOTH 2.9

    So... if I'm correct, BOTH primary windings are out... The owner of the shop i went to said he'd been doing bikes for 51 years, and said he'd never seen both coils fail on a bike before... But what am I to tell him? The multimeter doesn't lie, does it? To tell the story of my ignition system is a long one... I've experienced a few shorts in the ignition system, blown fuse a few times, and arc'd a few times due to stupidity, from the metal positive connector for the solenoid to the frame. My hand is much steadier now..

    Has anyone else seen both coils fail before? I am going to order fresh, brand new ones if nobody stops me.

    Thanks!
     
  9. Jetfixer

    Jetfixer Well-Known Member

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    I run Honda CB750 coils these have replacable plug wires they mount in same location as stock. Can still be bought new 39 each from Cycle Recycle part 2 they also sell wires and caps. So I take bike will not start? What condition are your coils in? Are there any cracks in the case?
     
  10. XJ550H

    XJ550H Well-Known Member Premium Member

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    did you ohm out the sparkplug caps?
     
  11. DoubleTigerLefty

    DoubleTigerLefty Member

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    They look great! I've deduced why they may have failed. In testing for the spark, I may have not kept the plug grounded when i took it out of the head. So I suppose that may have been a p;roblem for the primairy windings, not giving them anywhere to go, and it may have happened just too many times. So now my coils are 2.9 - 3.

    As for the caps, they're all 4.9, I've rep;laced the stock ones with NGK's.

    However, when i measure at the caps when they're still connected, I get something like 21.9 on the secondaries if I recall correctly. I am getting coils either off fleabay or off a gracious member who lives near enough to me. And then I'm buying that lottery ticket so I can buy you all beer for help;ing me with my moronic past self's mistakes.
     
  12. May_J_Aaron

    May_J_Aaron Josh May

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    Is there a specific year or model of CB750 that would match?
    I have an 83 Maxim 750.
     
  13. XJ550H

    XJ550H Well-Known Member Premium Member

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    May_J_Aaron likes this.
  14. Jetfixer

    Jetfixer Well-Known Member

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    The 81 to 83 ...cycle recycle part 2 sells these coils new they also carry wires and caps ..the coils are like 39$ each last I looked ...there place looks like a strong wind would blow it down ...but it is floor to ceiling with old bike parts .
     
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  15. May_J_Aaron

    May_J_Aaron Josh May

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    So I get about 3.1 OHMS at the pigtail when testing it which is good but when testing the wire, positive in the cap making metal to metal contact, negative in the pigtail with the voltmeter set to 20k I don’t get any reading...
    Is there a different way of doing it?
    6123CDD5-DF95-45C5-B5D9-5849B22035F4.jpeg
    76E82972-94B4-44D5-89C1-921E24E6EB65.jpeg
    obviously I don’t test it 1 handed but just to show how I’m doing it.
    I’m also aware that left coil is 1 & 4, right is 2&3.
    Am I doing this right? It’s what I saw on YouTube...
     
  16. Rooster53

    Rooster53 Well-Known Member Premium Member

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    You need to check the ignition coil secondaries by measuring from cap to cap. Set the meter to 200K if the caps are on as the expected reading will exceed 20K when adding the 5K for each cap. You can use the 20K scale if you remove the caps as the reading should be about 11k ohms.

    https://www.xjbikes.com/forums/threads/the-information-overload-hour.27544/

    For all XJ models except XJ700, XJ750-X, and XJ900 models:

    Primary (input from TCI): 2.5 ohms +/- 10%
    = 2.25 ohms - 2.75 ohms acceptable range

    Secondary (output to spark plugs): 11K ohms +/- 20%
    = 8,800 ohms - 13,200 ohms acceptable range

    5K +/- 20% = 4,000 to 6,000 ohms per cap acceptable range:
    all XJ650 models
    1985 XJ700 air-cooled models
    all 1981-84 XJ750 (except XJ750RL) models
    all 1983-84 XJ900RK and RL models
    all XJ1100 models
    all XS1100 models
     
  17. Polock

    Polock Well-Known Member

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  18. XJ550H

    XJ550H Well-Known Member Premium Member

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  19. May_J_Aaron

    May_J_Aaron Josh May

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    It’s worth paying a little extra to know it’ll work!
    Looks like it would allow the plug wires to be changeable as well which is nice!
     
  20. XJ550H

    XJ550H Well-Known Member Premium Member

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    dynatek coils are not direct bolt ons you will have to make an adaptor or buy it from xj4ever
     

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