Testing Stick Coils on R1200GS - need clarification

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

  1. davidmc

    davidmc Been here awhile

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    Hi Folks,

    I need to check the stick coils on my 2008 R1200GS with 85,XXX miles this weekend and I am looking for some clarification to the procedure. I have searched many threads and there are some conflicting ideas on how to do it.

    My understanding is that the bike will run on one set of coils and to test the coil, you unplug the opposite coil and see if it still runs. For example to test the primary coil, you would unplug the secondary coil and if it runs poorly the primary is bad. If you unplugged the primary coil and it ran poorly the secondary plug was bad.

    Is this correct? I saw a couple of other posts that said if you unplug a coil and it still runs then THAT SAME coil is bad, which makes no sense to me at all.

    I am also under the impression that you should only unplug the coil at the connector wiring plug and never remove the tip from the spark plug when doing this test.....is this also correct?

    Thanks in advance for any tips on this, I know there has been previous discussion on this topic, but these coils are expensive if something goes wrong so I want to do this the right way.
    #1
  2. Swinefahrt

    Swinefahrt RooteR

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    :ear
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  3. ragtoplvr

    ragtoplvr Long timer

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    The stick coil the low voltage lead is easily unplugged. If no RPM change then it is bad. Never run it with the coil unplugged from the spark plug. The secondary coil is hard to reach the low voltage connection. So, with the engine off, unplug the spark plug lead and use a old spark plug plugged in to the lead or some kind of wire that hits the metal terminal inside the spark plug lead and ground it. If the stick coils are bad it will not run, and this will protect your coil.

    Rod
    #3
  4. Beezer

    Beezer Long timer

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    edit. ooppp sorry.... wrong bike forget that
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  5. marchyman

    marchyman DR and GS

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    :confused in series?

    Primary coil and secondary coils are fed from different pins of the BMS K. Both coils on a side are tied to the same ground.
    #5
  6. SR1

    SR1 Back in S. Korea

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    The bike will run on a SINGLE coil in ANY position. Search for my coil thread. There is not always a definitive way to identify the bad coil, unfortunately. mine was truly guesswork.
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  7. GP1200

    GP1200 Been here awhile

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    I tried all these methods as well. Just unplugging one at a time without riding the bike will not help you. It's amazing how well the bike runs on just one good coil in a cylinder at idle. Also, a coil may produce a spark outside the cylinder but fail inside the combustion chamber under load. A trick the dealer has is a temperature gun pointed at each cylinder when warm. A cylinder with one faulty coil will run much cooler than the other. A GS-911 should show cylinder temps too.
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  8. SR1

    SR1 Back in S. Korea

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    Point 1, you're right, but you can also (with my issue at least) ride the bike with one or a couple of coils unplugged and not determine the bad coil.

    Point 2, I wish I had looked at this parameter on my GS-911. I didn't think to try it. Now I have spare coils around :cry but it is a good idea.
    #8
  9. DSTEVENS

    DSTEVENS Been here awhile

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    OK, while we are talking about stick coils, will they cause misfiring and backfiring when cold started but then bike runs good when warm. 13 GSA 6200 miles, hasn't had 6000 service yet. Just wondering. D.
    #9
  10. JimVonBaden

    JimVonBaden "Cool" Aid!

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    Not usually. The coil is more likely to work cold and miss hot. Misfire cold is either the intake temp sensor or an O2 sensor most likely.

    Jim :brow
    #10
  11. GP1200

    GP1200 Been here awhile

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    My coils were fine and not the problem, so when I disconnected one, especially the primary, it was very noticeable when riding the bike but not at idle. I found it to be a bit dangerous in traffic too because you lose power. Try the temperature trick first. The BMW tech said the cylinder with the faulty coil can vary by as much as 70 degrees F .
    #11
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  12. Crazy Al

    Crazy Al Namaste

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    I thought I had a bad coil because the engine was breaking up at the high end. I replaced with a set I knew was good from a buddy and the engine still broke up. I dragged it into Countryside BMW in my area for a diagnostic (quick service and cheaper than anticipated) and was told it was the connector to the stick coil and that there was a service bulletin about same. Took it home (rode it there and back as it only broke up under heavy load) and indeed the left bank connector (top coil) was corroded and separating at the middle - reminded me of a hinge. The replacement was back ordered from Germany but the good folks at the parts counter phoned me the next day, finding one in CA. I received it in a couple of days and installed it. Of course it was the same connector and a tight soldering job. Bike had about 45k at the time. Still running fine with about 70k.
    #12
  13. SR1

    SR1 Back in S. Korea

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    Man you ain't kiddin'! It nearly launched my wife and I off the bike the first time it did it...I was hard on the throttle and it was lurching like crazy. Glad I got it fixed last year.
    #13
  14. JimVonBaden

    JimVonBaden "Cool" Aid!

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    Just an FYI, I had a Camhead on the GS911 today and the head temps run nearly dead on. So any variation in temps could definitely be an indicator of a stick coil not working at idle, and at off ide.

    Jim :brow
    #14
  15. DSTEVENS

    DSTEVENS Been here awhile

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    Thank you Jim, it runs terrible when cold, but runs fine after it warms up. Hasn't been ridden since August. Wish you were not so far away:D. D.
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  16. GS Addict

    GS Addict Pepperfool

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    Q: Isn't the O2 sensor out of the equation until the engine warms up (open loop)?
    It's that way on the oilheads.
    #16
  17. JimVonBaden

    JimVonBaden "Cool" Aid!

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    There are others with a better understanding, but according to the GS911 that is not the case on the Camhead. :dunno

    Roger?

    JiM :brow
    #17
  18. Steptoe

    Steptoe steptoe

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    Very simple and easy to test the coil sticks..

    Disconnect the lower coil connection from EACH side so you're only running on the main plug on each side.
    If the bike fires and runs ok (if one of the main coils has failed completely the bike will only fire on one side) then take if for a quick 5 minute ride, and make the engine labour by using a higher gear than normal to check if one is failing under load.

    If all is ok reconnect the lower coils and then do the same procedure with the main coils.
    #18
  19. GP1200

    GP1200 Been here awhile

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    Sorry, your method is not simple or easy. I've tried it. Can't bite my tongue on this one. Your bike will run like shite every time you disconnect any coil . I don't have a "relative shite meter" You better ride the bike away from any traffic because it's also dangerous as the bike loses power and surges like crazy. And how will your method determine which cylinder is the culprit?
    Even with the temperature test , you'll still have to determine if it's the primary or secondary coil that's bad.
    The easiest and safest way is to check the temperature and have donor coils from a friends bike to determine if it's primary of secondary.
    If your "disconnect " method works for you, then great. As an average DIYer it did not achieve my goal.
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  20. roger 04 rt

    roger 04 rt Long timer

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    Edit with data and re-post

    I've got a lot of cold start data from Terry's 2010 R1200GSA. Although the sensor has to be hot before closed loop, the Bosch hardware patents and O2 heater get closed loop going in about 40 seconds. The intake, engine and oil could be fairly cold.

    Edit:
    One morning last spring Terry's bike was 50F. 15 seconds after he started, the bike was running closed loop. Oil and Cyl temps still 50F. The quick time to closed loop surprises me.
    #20