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Thread: I Suspect this Abnormal Noise is Normal

  1. #1
    Registered User andreb's Avatar
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    I Suspect this Abnormal Noise is Normal

    I have recently noticed a weird noise coming from my K1600GT. In normal riding, I never hear anything or feel anything. It first happened while riding some great paved twisty roads in the South Dakota Black Hills, I am speeding up and down, rowing the gearbox and using the throttle with great gusto (what fun!). It was like I was on a racetrack.

    At the point of a hard shift, I hear a loud drivetrain thunking or abbreviated backfire (a backfire that starts but gets only partially out the tailpipe) but I can't tell which. Or perhaps it resembles some large valve or rubber poppet shutting and opening, I cannot pin down where it is specifically coming from. I am not using the brakes when it happens. The bike is accelerating without a hitch and is completely stable without any stumbling, hesitation or instability. I feel absolutely nothing in the drivetrain and engine, it is all auditory. I can reproduce the noise by riding hard.

    Is this noise evidence of the traction control in action? I have had automobiles with traction control and they are silent. It is unlike anything I've ever heard. My dealer did not have a ready explanation.
    Andre Boening
    2010 F800GS and 2012 K1600GT

  2. #2
    Registered User lkchris's Avatar
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    Does the K16 have a "flapper" in the exhaust system, like say the '10-on boxers?

    On those bikes, anyway, it's a cable-controlled flap that opens/closes the size of the pipe a bit.

    I've yet to ride a bike with one, so just speculating.
    Kent Christensen
    21482
    '12 R1200RT, '02 R1100S, '84 R80G/S

  3. #3
    Registered User dmftoy1's Avatar
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    If its traction control you'll see a flashing yellow wheel on the left side of your dash for a couple of seconds. No clue about your noise. I can't say I've experienced it on mine.

  4. #4
    Registered User mneblett's Avatar
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    Purely speculation, but I'm betting it is a noise from the slipper clutch set up.

    Not only does the clutch have a slipper function which tries to prevent rear wheel lock-up/sliding when the engine speed doesn't match road speed after a downshift, the same ramps are engaged in the opposite direction under hard acceleration to add additional clutch plate engagement force. I suspect what you're hearing is relative motion between the opposing ramps in the clutch hub.
    Mark Neblett
    Fairfax, VA
    #32806

  5. #5
    Registered User andreb's Avatar
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    Update

    Here are some comments in response to your useful thoughts. They have at least helped me to discard (I think) potential causes.

    There might be a flapper valve, but I read no mention of any flapper valve in my official K1600 Reprom, not did I notice any separate flapper valve in the parts list. I have not noticed any yellow warning lights flashing on my dash. Maybe it is the slipper clutch, but I have not noticed any similar noise (actually no noise at all) when forcing the slipper clutch to work by performing a downshift and not revving the throttle to match up engine/transmission speeds. I make a point of shifting smoothly, but swiftly, I avoid invoking the slipper clutch. Of course, I feel nothing in my hands, seat or feet.

    I suspect it is a combination of the multiple actions by the traction control, like shutting off the engine, modulating brakes, unloading the transmission and then loading the transmission (gear lash) and who know what else. Perhaps I need to read a good explanation of BMW's take on traction control.
    Andre Boening
    2010 F800GS and 2012 K1600GT

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