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Thread: Ignition coil resistance check.

  1. #1
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    Ignition coil resistance check.

    Chasing a hard start on 2004 XB. Measured primary and secondary side of the ignition coil. Measured 1.3 - 1.4 Ohm on primary and ~11,700 Ohms on the secondary. According to the manual both are way out of spec, primary should be 0.5 to 0.7 and secondary 5.5k and 7.5k. Kind of odd both sides are jacked on mine. Would appreciate some one would check their coil on 04 model.

    Also sprak plug wires are reading ~180 ohms or so.

    Attached is a picture of how I checked the windings.

    Last edited by cossack84; 12-21-2019 at 07:06 PM.

  2. #2
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    Update to help the next guy. I received a new coil and spark plug wires, but new coil still measured same resistance. The picture in owners manual is somewhat confusing, if you use bottom portion as a reference guide then the reading you get are going to be double of what the spec is, just like mine was. I measured primary side and secondary side in series. But after rereading and trying to figure out why original measurement was double of spec, I come to find out that one needs to measure each winding individually. Manual specifications are for each winding individually and should be measured off the common lead on the primary side, where connector clips in from the wiring harness.
    What my problem turned out to be was the spark plug wires. Reading on those was a lot lower than what manual have specified.

    Last edited by cossack84; 12-28-2019 at 03:30 PM.

  3. #3
    Senior Member lunaticfringe's Avatar
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    somewhere early on H-D archives and publication division transposed "single fire coil" trouble-shooting schematics and instructions with both XB and sportster "dual fire coil" SM schematics and instructions. all XB coils of course are a "wasted-spark" design...which is "dual fire".
    this has been discussed at length on here...which you failed to research.
    also addressed and resolved via Technical Service bulletin TSB-B-041-C......late 2004...which can be found with simple search @ www.harley-davidson.com

    TSB also included non-verbatim: "for ignition related rideability problems/complaints simply replace F&R spark plugs and F&R spark plug wires. if same problem persists then additionally replace ignition coil."
    Last edited by lunaticfringe; 12-30-2019 at 02:12 PM.

  4. #4
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    Dual fire, that's why there are separate coils for each cylinder on primary / secondary side, and a separate timing table. Put down the pipe.

  5. #5
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    XB coils are single-fire, not wasted spark. This has been confirmed by Dan (Director of Engineering) at Buell/EBR.

    If they were wasted spark (dual-fire), you could remove one of the signal wires and both plugs would still fire. Spoiler, they don't.
    Last edited by jetlee; 12-30-2019 at 02:53 PM.

  6. #6
    Senior Member mmcn49's Avatar
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    My $.02.

    -Ignition coils do fail but rarely.
    -To measure low resistance, (below 10 Ohms) you need a very expensive Low Resistance Ohmmeter.
    -Buell's use Carbon Suppression wires.
    -These break down over time increasing resistance and reducing spark energy.
    -IMO these should almost be considered as maintenance items.
    -Spiral wires are long lived and tend not to break down as quickly as carbon.
    https://www.magnecor.com/magnecor1/truth.htm

    As John stated replacing plugs and wires will resolve most ignition issues. Years ago I replaced the stock wires with spiral automotive wires and they've worked great for 40+K on one Buell and 20+K on the other.

  7. #7
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    Quote Originally Posted by jetlee View Post
    XB coils are single-fire, not wasted spark. This has been confirmed by Dan (Director of Engineering) at Buell/EBR.

    If they were wasted spark (dual-fire), you could remove one of the signal wires and both plugs would still fire. Spoiler, they don't.
    Thank you, some one who understands what they are looking at / dealing with, not simply regurgitating nonsense.

  8. #8
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    Quote Originally Posted by mmcn49 View Post
    My $.02.

    -Ignition coils do fail but rarely.
    -To measure low resistance, (below 10 Ohms) you need a very expensive Low Resistance Ohmmeter.
    -Buell's use Carbon Suppression wires.
    -These break down over time increasing resistance and reducing spark energy.
    -IMO these should almost be considered as maintenance items.
    -Spiral wires are long lived and tend not to break down as quickly as carbon.
    https://www.magnecor.com/magnecor1/truth.htm

    As John stated replacing plugs and wires will resolve most ignition issues. Years ago I replaced the stock wires with spiral automotive wires and they've worked great for 40+K on one Buell and 20+K on the other.
    Your post make sense after I figured out how one should measure a coil to properly diagnose its condition. Fluke 789 is fairly good quality meter that I feel confided in measuring deference between 0.5 ohms and 1.4. Bike had some sort of aftermarket wires that measure way under the book specification, around 180 ohms. I replaced them with OEM just because I was placing an order for a coil and they happen to be in stock. Next time I need a new set of spark plug wires I'll give your recommendation a look. Thank you!

  9. #9
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    Quote Originally Posted by lunaticfringe View Post
    this has been discussed at length on here...which you failed to research.
    Ok Mr. Wasted-park, find a post that shows an internal wiring diagram of the ignition coil, tells you how to properly measure primary and secondary coil resistance, measure it in series or individual and spec for each coil. Also what those readings mean.


    Edit:

    This is gold,

    TSB also included non-verbatim: "for ignition related rideability problems/complaints simply replace F&R spark plugs and F&R spark plug wires. if same problem persists then additionally replace ignition coil."

    Any retard can simply keep replacing parts until bike starts running again. It takes brains, I know, shock, to be able to properly troubleshoot.
    Last edited by cossack84; 12-31-2019 at 02:29 AM.

  10. #10
    Senior Member mmcn49's Avatar
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    Quote Originally Posted by cossack84 View Post
    Your post make sense after I figured out how one should measure a coil to properly diagnose its condition. Fluke 789 is fairly good quality meter that I feel confided in measuring deference between 0.5 ohms and 1.4.
    You generally can't get accurate “Low Ohm Measurements” even with a good quality VOM. On the Primary Winding the only thing you can check with a VOM is continuity.

    Quote Originally Posted by cossack84 View Post
    Bike had some sort of aftermarket wires that measure way under the book specification, around 180 ohms. I replaced them with OEM just because I was placing an order for a coil and they happen to be in stock.
    If your resistance readings are accurate, they are probably spiral suppression wires. If so they are still good and superior to the stock carbon suppression wires you just purchased.

    Quote Originally Posted by cossack84 View Post
    Ok Mr. Wasted-park, find a post that shows and internal wiring diagram of the ignition coil, tells you how to properly measure primary and secondary coil resistance, measure it in series or individual and spec for each coil. Also what those readings mean.
    TSB also included non-verbatim: "for ignition related rideability problems/complaints simply replace F&R spark plugs and F&R spark plug wires. if same problem persists then additionally replace ignition coil."


    Quote Originally Posted by cossack84 View Post
    Any retard can simply keep replacing parts until bike starts running again. It takes brains, I know, shock, to be able to properly troubleshoot.
    John is well liked on the Forum. He is extremely knowledgeable and goes out of his way to help other members like you. He told you exactly what you needed to do to get the bike running. Many here have skills in various areas and help out when they can. Most here are good people, no one likes to be insulted.



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