Sudden full throttle and engine pinging noise

    Today I noticed that if I turn suddenly full throttle, without engaging any gear, I can hear for a couple of seconds the engine pinging before smoothing out. If I’ll do exactly the same thing but just a bit slower the engine revs up smoothly all the way up. Although I ride the bike for almost 8 years now I am not able to say if this is something new. For the last couple of years it has been coming out of the garage only during dry weekends so I might start to forget things…


    Thank you for your patience
    Stavros


    K75 S 1989 (127.000km)

    Dear Stavros,


    although I never heard a real pinging noise on any of my K´s I think if it does not run up smoothly as you mentioned its just to check the classical wellknown things first, such as
    1. possible leakage in the air intake system, most probably always first choice in such situation; check and correct if needed.
    2. missing or bad synchronizatioin between the cylinders air intake; synchronization should be repeated anyway if any air leakage has been found and only after it has been fixed!
    3. bad adjusted idle switch might also influence such behaviour; check wether you hear a sligt klick when touching throttle just a little bit from zero position, if not, adjust (its located at rear end of throttle system).
    4. last but not least; check the fuel filter wether too old and possibly partly closed from dirt.


    Good luck


    Bernhard

    Thanks Bernhard.
    I 'll follow your suggestions and I'll give you the feedback.


    Stavros

    Zitat von "Goldentie"

    I turn suddenly full throttle, without engaging any gear


    What's the reason for doing that? :shock:

    Heinz
    "Technischer Fortschritt ist wie eine Axt in den Händen eines pathologischen Kriminellen."
    Albert Einstein

    Ha!


    Dear Heinz, I knew you would ask that!


    Well it's an old habit of mine when riding the good old airhead (a 1983 R65) blipping the throttle while downshifting. Sometimes I find myself doing the same while riding the K75 and that's when I noticed the brief rattle coming from down below. In order to check the ''symptoms'', (if any) I parked the bike on the side of the road and I played a bit with the throttle giving a couple of quick turns.


    That's all for the moment, I hope I'll have some news in the morning.


    Thank you once more,
    Stavros

    It's exactly the same on my K75C and always has been.


    I wouldn't describe it as "pinging" exactly, but I think the noise must be caused by the crank shaft speeding up rapidly and the long timing chain throwing a wobbly as it tries to emulate the crankshaft rotational speed. You know how a drive chain flaps up and down on a racing bike when viewed in slow motion, well I have a feeling that that's what is happening to the cam chain.


    As it catches up, the vibrations disappear and the noise disappears. As you say, it only happens with a very rapid opening of the throttle from tickover. If the revs are higher and you do it, then you don't get the noise.


    I think they call it inertia ..... but I stand to be corrected.

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