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Thread: Slipper Clutch and Friction Zone

  1. #31
    Dress for fall & avoid it AlanColes's Avatar
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    Quote Originally Posted by ncpbmw1953 View Post
    Alan, I said nothing about 'cold engine oil' vs 'engine oil at proper operating temps...' that is your reframing of the point I was making.

    What I did say was that on a COLD START at AMBIENT of maybe 66F and up you get the clunk IMMEDIATELY, before engine oil or transmission has changed appreciably, whereas as below that you don't get the clunk until the engine runs for a few minutes. This suggests the source of the major difference is more to do w/ expansion of the parts involved, versus 'acoustic dampening differences' from changes in the oil. You're comment seems to suggest when OIL temp is 62F, major dampening happens, whereas when OIL temp is 66F minimal dampening effects are happening. No way, no how! It's as you mentioned later, 'Spacing of parts, spin-down and spin-up times, etc., all change as the transmission heats up and when completely cold' is essentially what I said in other words, 'My sense is that as parts heat up tolerances are tighter such that one rotating part starts to get dragged into turning by another adjacent gear/part, and so this creates the clunk that worsens as the bike warms.'
    My misunderstanding/misreading. I was thinking that your clunk was like mine, most pronounced at cold startup (oil at ambient (60F-80F mostly) and not after the bike has been run for a while (oil at 180F-210F).
    Regards, Alan - President BMWONS - MOA Charter Club #097, BMWMOA/BMWRA/BMWONS/Airheads
    Current: '14 R1200RT / '06 Ducati ST3s / '91 R100GS / '86 R80RT / '75 R90S / '73 850 & '70 750 Commando Prev: '04 R1150RT / '81 Honda GL1100 / '77 Suzuki GS750 / '73 Norton 850 Commando

  2. #32
    Fortis Fortuna Adiuvat Omega Man's Avatar
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  3. #33
    Quote Originally Posted by ncpbmw1953 View Post
    Alan, I said nothing about 'cold engine oil' vs 'engine oil at proper operating temps...' that is your reframing of the point I was making.

    What I did say was that on a COLD START at AMBIENT of maybe 66F and up you get the clunk IMMEDIATELY, before engine oil or transmission has changed appreciably, whereas as below that you don't get the clunk until the engine runs for a few minutes. This suggests the source of the major difference is more to do w/ expansion of the parts involved, versus 'acoustic dampening differences' from changes in the oil. You're comment seems to suggest when OIL temp is 62F, major dampening happens, whereas when OIL temp is 66F minimal dampening effects are happening. No way, no how! It's as you mentioned later, 'Spacing of parts, spin-down and spin-up times, etc., all change as the transmission heats up and when completely cold' is essentially what I said in other words, 'My sense is that as parts heat up tolerances are tighter such that one rotating part starts to get dragged into turning by another adjacent gear/part, and so this creates the clunk that worsens as the bike warms.'
    BMW motorcycle transmissions clunk. They always have. Some less than others but they clunk. In 1977 I got off a Yamaha triple and onto an R60/5. The first time I shifted from 1st to 2nd I actually looked back and down to see what had broken and fallen off the bike.
    Paul Glaves - "Big Bend", Texas U.S.A
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  4. #34
    Quote Originally Posted by PGlaves View Post
    BMW motorcycle transmissions clunk. They always have. Some less than others but they clunk. In 1977 I got off a Yamaha triple and onto an R60/5. The first time I shifted from 1st to 2nd I actually looked back and down to see what had broken and fallen off the bike.
    Apparently BMW decided enough people found their proprietary clunk objectionable enough to make revisions for at least some 2017 water boxer designs. Good for them as there is nothing inherently pleasing about clunking transmissions, especially the N>1st gear clunk.

  5. #35
    Dress for fall & avoid it AlanColes's Avatar
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    Quote Originally Posted by ncpbmw1953 View Post
    ... people found their proprietary clunk objectionable ...
    While folks might like to categorize things this way, it is not the case. Nothing proprietary about it.

    Quote Originally Posted by ncpbmw1953 View Post
    ... Good for them as there is nothing inherently pleasing about clunking transmissions, especially the N>1st gear clunk.
    For/to you. But that isn't everyone.

    I have no such aversion to the relatively un-muffled sound of the BMW transmission, I actually prefer it's honesty.

    BMW transmissions are known to last as long or longer than most.

    Perhaps haven't ridden many touring Harleys. Like BMWs, they will happily rack up hundreds of thousands of worry-free miles but the trannies have a very definite audible clunk to them. They are just doing their job with less muffling than other makes.

    No one is forced to buy one, but also, no one should really complain about something that has been a known fact for decades. Buy Honda and you'll know you've shifted gears when the gear-indicator confirms it - that's a gross exageration, but there is a real difference just like there is with the Boxer engine. I had a Gold Wing but perfer the BMW Boxer to the Honda Boxer. If a person doesn't like the basic characteristics of a specific vehicle why did they buy it in the first place? Well, sometimes it takes owning/riding several bikes until we identify what it is that we like the most and what we don't care for or want. There are plenty of choices out there and most all of them are very good bikes, just different approaches and flavours, which is absolutely great for all of us.
    Regards, Alan - President BMWONS - MOA Charter Club #097, BMWMOA/BMWRA/BMWONS/Airheads
    Current: '14 R1200RT / '06 Ducati ST3s / '91 R100GS / '86 R80RT / '75 R90S / '73 850 & '70 750 Commando Prev: '04 R1150RT / '81 Honda GL1100 / '77 Suzuki GS750 / '73 Norton 850 Commando

  6. #36
    not so retired henzilla's Avatar
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    Quote Originally Posted by PGlaves View Post
    BMW motorcycle transmissions clunk. They always have. Some less than others but they clunk. In 1977 I got off a Yamaha triple and onto an R60/5. The first time I shifted from 1st to 2nd I actually looked back and down to see what had broken and fallen off the bike.
    My first Oilhead ride had me a bit worried I broke H's bike

    I think the biggest clunk I have experienced is a K 1200 Wedge idling high at start up and nudging it into 1st....EVERYONE turns to look I mean CLUNK And it's a wet clutch as well.

    I have ridden several Wetheads and haven't thought about it at all.
    Steve Henson
    SABMWRA MOA Club#62's Flat Fixer/ current forum moderator
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  7. #37

    Clunk or Hop, that is the question?

    As the bard from Avon once said, to be or not to be, that is the question! Well this this thread has drifted mightily to clunk or not to cluck, is that a question??? Lots of bikes clunk. Some more so and others less. Really I am much more concerned about how well they shift, and does the clunk cause a problem with shifting. Although we have danced around this but how the transmission is designed and built has a lot to do with it. All the bikes I have ridden, if you pull in the clutch, you still get the clunk so the clutch usually isn't the clunk culprit. That's my 2 cents.

    Now, as the OP, the real issue was the hopping problem directly related to clutch activation. IMO, this issue was resolved as a design issue known to BMW. Also, IMO, it is a potentially dangerous situation and worthy of a report to the NHTSA.
    Old But Not Dead
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