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Thread: Misses at WOT

  1. #1
    RIDEOREGON
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    Misses at WOT

    My '07 RT---I went to pass a vehicle yesterday and wanted to get around them 'quickly'. I started acccelerating and pegged the throttle. The rpm's began to climb and then the motor started cutting out. I've been able to duplicate the symptom---whack the throttle wide open and watch the tach. When the rpm's get to about 5000 the motor will start missing. Interestingly, if I gradually let the rpm's rise it will not do this--only when I really peg the throttle wide open. Any ideas what's going on??

  2. #2
    Small road corner junkie pffog's Avatar
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    Spark plugs or weak spark

  3. #3
    A bozo on the bus deilenberger's Avatar
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    I'll add to that just a bit..

    Bad plug
    or
    Bad coil

    Either will cause this symptom. The first is easy to eliminate - put all new plugs in. The second is harder since you have to test by replacement usually.
    Don Eilenberger http://www.eilenberger.net
    Spring Lk Heights NJ NJ Shore BMW Riders New Sweden BMW Riders
    '07 R1200R (current ride) and some bimmers.. and a Porsche

  4. #4
    Registered User mpmarty's Avatar
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    I found a "handy dandy" coil tester at the local farm co-op. It is an electric fence tester and gives a good visual indication of the voltage on a fence or a coil. You ground one end and let the plug wire touch the other end and crank the bike over you can also do this with a spark plug on the end of the wire resting the plug on the head so it is grounded. You then watch for a fat blue spark at the plug. I absolutely hate diagnosis by replacement. Too costly and it's like shooting in the dark until you hit the target by pure dumb luck.
    Marty - in the western Oregon mountains.'06RT, (gone '04RT, '86 Venture Royal, '81 Yamaha Virago920, '82Suzuki GS1100GK, '76 Suzuki GT750, Triumph 750 Bonneville, BSA Road Rocket 650, 61" Harley knucklehead)

  5. #5
    A bozo on the bus deilenberger's Avatar
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    Quote Originally Posted by MPMARTY View Post
    I found a "handy dandy" coil tester at the local farm co-op. It is an electric fence tester and gives a good visual indication of the voltage on a fence or a coil. You ground one end and let the plug wire touch the other end and crank the bike over you can also do this with a spark plug on the end of the wire resting the plug on the head so it is grounded. You then watch for a fat blue spark at the plug. I absolutely hate diagnosis by replacement. Too costly and it's like shooting in the dark until you hit the target by pure dumb luck.
    Ummm... with a coil on plug design - how are we using this?

    Champion made an ignition tester that worked the same way - metal end you put on an ignition wire, with a neon bulb attached. Bulb flashed with the spark.. I have one, but never really saw a way to use it with a coil on plug design. Doing a free-air test of a plug/coil IS different from doing a test with compression pressure trying to blow the spark out.. That mistake has caught me once REALLY good - I never made that mistake again..
    Don Eilenberger http://www.eilenberger.net
    Spring Lk Heights NJ NJ Shore BMW Riders New Sweden BMW Riders
    '07 R1200R (current ride) and some bimmers.. and a Porsche

  6. #6
    Small road corner junkie pffog's Avatar
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    Setting the plug on the head is virtually useless to diagnose a partially fouled plug or weak spark.

    I have seen numerous professional mechanics spend hours trying to diagnose intermittent running problems, because the plugs looked good or were NEW. Only to install fresh plugs and fix the problem.

    I started working on engines when I was 12 (42 years ago), and was a MC/auto service manager for over 20 years, and I can tell you spending $10 on a set of plugs is NOT diagnosis by replacement, it is the ONLY way to "test" plugs. And if it fixes the issue, it will be the best $10 he spent. If it doesn't, my bet is still ignition probably weak spark. And if nothing else he will have a new set of plugs for his next tune up.

  7. #7
    TravelsWithBarley.com
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    I had the exact same symptoms and it turned out to be a cracked insulator on one of my plugs.
    '07 R1200GS for solo rides
    '10 R1200GSA with Hannigan dual sport sidecar for rides with Barley

  8. #8
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    Misfire

    I had a 5000 rpm, 6th gear misfire on my 07 R1200 ST. The only time it would do it was when accelerating through that RPM range. Changing all four plugs cured it.

  9. #9
    Small road corner junkie pffog's Avatar
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    the other thing that was not mentioned was water in the fuel, very common and could cause similar symptoms.

  10. #10
    Toadmanor
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    All four plugs?

    How many plugs are on a R1200 RT?

  11. #11
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    Four. 2 per cylinder. One in the middle, one lower.
    2013 Triumph Trophy
    2007 R1200RT Broken driveshaft @ 54,000 miles. Come on BMW!
    2000 R1100rt sold @ 72,000 Great Bike!
    Iron Butt #24605

  12. #12
    Cam Killer marchyman's Avatar
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    People seem to miss the lower plugs on the hexheads. why

    It's on the bottom side of the cylinder. Here's a pic from my '05 GS.



    Hanging below the plug is the lower coil inside the plastic shroud that protects it.

  13. #13
    RIDEOREGON
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    New plugs. I'm all good now. Thank you forum members!

    On a side note: I installed the BMR pilot shelf for my Zumo, GMX30, and Escort. Let me just say, it is "Farkle Bliss". A very nice and robust product!

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