Testing Stick Coils on R1200GS - need clarification

Discussion in 'GS Boxers' started by davidmc, Jan 9, 2014.

  1. Steptoe

    Steptoe steptoe

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    Fixing/repairing BMW's has been my living for the last 26 years :D And i do this test on many bikes on a weekly basis, most weeks more than once.

    The only reason it'll run like shite is if one of the coils has or is failing.


    You do realise we're talking about a 1200, which doesn't have a secondary or primary coil. It has 4 coil sticks.

    You can tell which stick has failed as that's the cylinder which doesn't fire or run properly as you're taking it in turns to run each cylinder in one coil stick. .
    #21
  2. GS Addict

    GS Addict Pepperfool

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    Not what I have found to be, Steptoe is right, I'm with him.
    You may actually have a bad coil.
    #22
  3. GP1200

    GP1200 Been here awhile

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    Good for you !!! Didn't say he was wrong, there are many ways to skin a cat ;)
    #23
  4. davidmc

    davidmc Been here awhile

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    Hey folks, thanks for the advice.

    So here is where I am. I disconnected both secondary coils at the connector and rode the bike with only the primary coils running. I rode it about 60 min, on the freeway and in town. It ran no different from when all 4 coils were connected and it may have even run a bit better.

    I also disconnected the primary coils and ran the bike with only the secondary coils connected. It ran fine at low speed, but when I put it under load going up a steep hill it barely ran at all.

    When I called the local BMW dealer to inquire about the availability of new coils they mentioned that the bike will not run on the secondaries alone and the stumbling would be normal. Apparently they test the coils by swapping coils to see how the bike runs. Would the bike be expected to stumble just operating on the secondary coils?

    I am strongly suspecting at least one of my secondary coils is bad, what do you guys think?

    And just to give you some background, my bike is surging and has a very snatchy throttle, mostly at low speed and rpms, which is why I am suspecting a coil issue.

    Thanks for any additional advice!
    #24
  5. GP1200

    GP1200 Been here awhile

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    Make an appointment at the dealer and make sure your bike is warm, have him check the temps of the cylinders. Or, a friends GS-911. it'll show up right away. Even better is borrow a friends primary and secondary coils and bring them with you to swap out the lower temp cylinder coils one by one. When the temp equalizes with the other cylinder, you've found the problem.
    Or you could unplug and re-plug coils all day long scratching your head and not getting anywhere.
    #25
  6. roger 04 rt

    roger 04 rt Long timer

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    davidmc, Per the above, I looked through your GS-911 logs, no temperature difference reported. However, I checked another rider's log, and both yours and his seem to always show the same CHT (exactly) for both cylinders.
    #26
  7. Steptoe

    Steptoe steptoe

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    :baldy
    #27
  8. InvisibleOrdinary

    InvisibleOrdinary Seeker

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    I'm trying to get a grip on understanding this, and have a couple questions...

    What happens if you run the coils unplugged and leave the spark plug in the cylinder head?...

    if you do leave the plug in, but have the coil hooked up and completing the circuit (something like a COP tester), this won't cause harm, correct?

    and in regards to testing them under load, wouldn't reving the engine while in neutral do the same as lurching about out on the street?

    Thanks

    Dave
    #28
  9. GS Addict

    GS Addict Pepperfool

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    All modern high energy ignition coils need need the spark plug in circuit to keep the voltage within acceptable limits.
    If the spark plug (the load) is not present the voltage rises extremely high and the voltage rating of the winding wire is exceeded and is usually permanently damaged.
    #29
  10. marchyman

    marchyman DR and GS

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    That is an ambiguous question. When you say "unplugged" do you mean unplugging the lead to the coil or do you mean unplugging the coil from the spark plug. If the former then you are testing if the coil is making a difference. If the latter GS Addict answered your question.
    #30
  11. InvisibleOrdinary

    InvisibleOrdinary Seeker

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    Thanks GS Addict, that makes sense... Didn't think that they would be that delicate, or maybe there's that much energy running through...

    @marchyman, suppose I didn't word that as clearly as I could have, but I was asking about what happens when you run the motor with the wire end (motor, battery) of the coil still plugged in to the coil, but the coil pulled off of the spark plug, with nothing re-inserted, or anything completing the circuit.

    Thanks
    #31
  12. pceire32

    pceire32 Irish

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    Would a bad coil be covered under warranty ?
    #32
  13. Eagerpooch

    Eagerpooch Been here awhile

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    I have been having issues with my 06 1200gs 15k mi remus exhaust. it stalls/hesitates at hard acc/load and also if on the highway in 5th and kicking it into passing mode. I changed all the top plugs about 2k mi ago and actually thought that fixed it but it has slowly come back and is bad again. I went ahead and changed the bottom plugs and that didnt do much. This brings me to think it may be the coils from the symptoms. I just did a trial ride unplugging various coils and this was the result. To be clear it runs way better with all of them plugged in. If i have a faulty coil i think it is only about 50% bad.

    Bottom 2 unplugged- hardly idles, rides okay at slow speed but sputters with any throttle. stalls when stopped

    Bottom R unplugged- runs much better (than 2 unplugged) sputters with harder acceleration

    Bottom L unplugged- hardly runs at all, stalls easy, sputters a lot under any acceleration (indicates a bad Top L coil)

    Top R unplugged- stalls pops, BACKFIRES bad runs like total sht

    Top L unplugged- stalls under heavy throttle, good at idle, can ride slow/tame

    I think all signs are pointing toward a bad top left coil (clutch side). Performance was really down when the top left coil didnt have the bottom plug to rely on. Also when the bike was set up with just relying on the top L and the bottoms it was crap
    #33
  14. orangelion56

    orangelion56 Adventurer

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    Eager: Nearly identical symptoms...have not done the coil check you describe. Did you fix the issue? Was it the top left coil and all is well now???
    #34
  15. Eagerpooch

    Eagerpooch Been here awhile

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    Hola Sir, yes it sure was that coil. i kept telling the dealer to make sure to check it and they said it wasnt that. well it turned to be and they were so apologetic for being such morons they replaced both coils free of charge.
    So do what i did. Start unplugging coils bec your bike will ride with only one good coil, itll just not run awesome. If you find that your bike runs like total shit or not at all then u know that the coil that is still plugged in on that side is the culprit. order a new one and be done. also just make sure your plugs look good. Bec when it runs like shit gook gets all over the plugs. my rig is awesome now. was an easy fix once figured out what it was.
    #35
  16. orangelion56

    orangelion56 Adventurer

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    Thanks for your response Eager! Tried the one-coil at a time check and they appear to be OK. At least at idle. Removed each one in turn, but there was only the expected change...a slight stumble as each one was removed, but went back to the normal lope when re-connected. Raining hard here so cant ride to test under loads. Maybe tomorrow...

    BTW, this was my original post: http://advrider.com/index.php?threads/rough-running.1195189/#post-31150431
    #36
  17. Eagerpooch

    Eagerpooch Been here awhile

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    yeah u may need to raise the RPMs. plugs are clean right? your symptoms are it runs fine but under heavy load like pinning it there is a stutter?
    #37
  18. orangelion56

    orangelion56 Adventurer

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    Putting in new plugs before further evaluation. Yeah, stutter under load in higher gears...roll throttle on slowly, no problem, but snap it open and it struggles. For example, on my road trip between Xmas and NYE, I was in 5th and uphill, dropped it into 4th to pass a car snapping the throttle open, it just stumbled until I rolled back the throttle a bit. Fortunately had plenty of room to complete the pass.
    #38
  19. Eagerpooch

    Eagerpooch Been here awhile

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    ya i think its the same problem. mine was the Left Main/top coil
    #39
  20. Steptoe

    Steptoe steptoe

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    You're not unplugging the spark plug cap, you're unplugging the power to the coil so there's no way any damage can be caused.

    I know this an old post i've quoted above but it's best to post the correct answer for future reference.
    #40
    JimVonBaden and vagueout like this.