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Thread: 2004 R1150RTP - noise on deceleration, what is it?

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  1. #1
    Registered User Badger7's Avatar
    Join Date
    Mar 2009
    Middleton, WI

    2004 R1150RTP - noise on deceleration, what is it?

    I'm soliciting your help to diagnose an engine noise on my 2004 R1150RTP with 110k. The engine runs great and smooth, but when using engine braking (decelerating with clutch engaged) the engine makes way too much rattling.
    I thought it would be the cam chain tensioner, but reading more on the "is this the dreaded death rattle" thread, it doesn't sound like that's it.

    I know I should just run it to the dealer for diagnosis, but my nearest one isn't very "near". And I'm wondering if I'm going to damage it by driving it there?
    Your input is appreciated.

  2. #2
    Registered User
    Join Date
    Jun 2003
    Northern Front Range, CO
    what kind of rpms are you running at that point?

    have you looked at tightness of all exhaust connections?
    Ride Safe, Ride Lots

  3. #3
    Probably just valve clatter. How long since your valve lash was adjusted?

    It's not the so-called death rattle of the left-side cam chain - I think they fixed that in the 1150 anyway. That only occurs at startup. And it is pretty much harmless, unless someone is there to hear it and say something that hurts your feelings.

    Perhaps it is making the rattle full-time and you can hear it when the throttle is closed because the intake and exhaust noise drops away?
    Sometimes I can adjust my windshield to a point where the motor noises are reflected back to me - might try that.

    Anyway the main thing that happens when you slam the throttle shut at relatively high rpms is that there is a dramatic decrease in the cylinder pressure. Also the throttle position sensor is now "lying" in that it says throttle is closed, minimal air flow, while in reality more air than that is actually being dragged in. So the ECM backs down the fuel - the result is a lean mixture that is not compressed properly, you get backfiring and that sort of thing. fixed as soon as you open the throttle again.

    Um, most likely thing to be rattling are the things with some rattle "required" - that's the valve rocker arms.

    At 110k there may be some wear on your actual valves. Sometimes this results in more lash, sometimes it results in less lash. More lash is a rattle, less lash usually results in the engine misbehaving when hot, if the valves don't close all the way.

    The valve clatter, particularly if the lash is too large, will have a resonant frequency, like any other thing in repetitive motion. So there will be an RPM value where the clatter is louder than anywhere else.

    Is too much lash harmful? - I don't think it is but I'm not sure.
    The sound is created by pieces of steel slamming together rapidly, which my primitive brain thinks is not good. But then, aren't they slamming together anyway? - just not bouncing around maybe.

    Excessive lash will change the valve timing slightly. They stay closed longer. Whether this is a good thing or a bad thing depends on too many variables for me.

  4. #4
    No longer a member here
    Join Date
    Apr 2006
    Clutch rattle.

  5. #5
    Quote Originally Posted by EMSimon View Post
    Clutch rattle.
    ??? hmm.
    Obviously I'm missing out, haven't experienced this.
    Of course I'm only at 80k.

  6. #6
    No longer a member here
    Join Date
    Apr 2006
    The R1150RT, like many BMWs, has an automotive-type, single plate dry clutch with torsion dampers (small springs) in the friction plate. If one (or more of them) brake, they cause a rattle in the drive train during load changes.

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