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Thread: what are the chances?

  1. #46
    Registered User lmo1131's Avatar
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    The truth is that in those days - can you say /5 - the sidestands were sufficiently self-retractingly crappy that the centerstand might have made sense.
    Yeah, useless they weren't... I stopped using the side stand the morning I drove off and it didn't self-retract as expected; it dug into the edge of the driveway and pitched the bike, and me, over the high side. Now equipped with a Brown's, I use the either stand as warranted by conditions at hand. And like jimmylee, I use the sidestand as "insurance" that I don't drop the machine when placing it up on the center stand.
    "It is what you discover, after you know it all, that counts." _ John Wooden

    Lew Morris
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  2. #47
    not so retired henzilla's Avatar
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    The non OEM sidestand on our /6 doesn't self retract and woke me up on the first left handed sweeper

    Even though not a "Airhead" in this conversation, putting the tiny bike on the centerstand on the 69S takes more effort than some LT's...it also has two sidestands. The bike is very upright on either.
    Steve Henson
    SABMWRA MOA Club#62's Flat Fixer/ current forum moderator
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  3. #48
    Benchwrenching PGlaves's Avatar
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    Quote Originally Posted by royce View Post
    So ... this question is from a "newbie", not to riding but new to BMWs: is that old adage true? I agree that BMW oldtimers rarely if ever park on the sidestand, but is it really true that they leak oil into the lower (left side) cylinder head? Or is it only lore? Perhaps used to be true, but no longer?
    When the engine is shut off it will usually stop turning with one piston coming "up" on the compression stroke. That cylinder will have both intake and exhaust valves closed. As the engine (and the air trapped in the cylinder) cools rapidly it creates a slight vacuum in the cylinder. That vacuum can draw oil past the rings if oil has pooled behind the rings. So on an Airhead or Oilhead on the sidestand there is some probability that the down side cylinder will be the one with the valves closed. Some smoking can happen.

    With any of the flop engine K bikes (75, 100, 1100, 1200) when on the sidestand there is a very high probability that one cylinder will be in the compression stroke, and thus one cylinder will have valves closed and the vacuum can draw oil past the rings. There was a reason my original K75 was named Old Smokey.

    The later K engines had the ring gaps pinned so they didn't all line up at the bottom of the cylinders. Early ones were not pinned, and I don't know when/if Airhead or Oilhead rings were ever pinned to block rotation.
    Last edited by PGlaves; 11-24-2013 at 10:22 PM.
    Paul Glaves - "Big Bend", Texas U.S.A
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  4. #49
    One big Oaff brewmeister's Avatar
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    What are the chances of pulling into a gas station to fill up and under the front tire is two crisp twenty dollar
    bills stuck together?
    I had to move the bike to retrieve them.
    81 R100RT

  5. #50
    sMiling Voni's Avatar
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    I'm not sure moving the bike was the best choice.

    Someone else might have grabbed them while you were still moving.

    Voni
    sMiling
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  6. #51
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    Quote Originally Posted by brewmeister View Post
    What are the chances of pulling into a gas station to fill up and under the front tire is two crisp twenty dollar
    bills stuck together?
    I had to move the bike to retrieve them.
    If you were at a MOA National, you'd have never had a chance.

  7. #52
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    Quote Originally Posted by PGlaves View Post
    When the engine is shut off it will usually stop turning with one piston coming "up" on the compression stroke. That cylinder will have both intake and exhaust valves closed. As the engine (and the air trapped in the cylinder) cools rapidly it creates a slight vacuum in the cylinder. That vacuum can draw oil past the rings if oil has pooled behind the rings. So on an Airhead or Oilhead on the sidestand there is some probability that the down side cylinder will be the one with the valves closed. Some smoking can happen.

    With any of the flop engine K bikes (75, 100, 1100, 1200) when on the sidestand there is a very high probability that one cylinder will be in the compression stroke, and thus one cylinder will have valves closed and the vacuum can draw oil past the rings. There was a reason my original K75 was named Old Smokey.

    The later K engines had the ring gaps pinned so they didn't all line up at the bottom of the cylinders. Early ones were not pinned, and I don't know when/if Airhead or Oilhead rings were ever pinned to block rotation.

    Just thinking of the physics of it, it made perfectly good sense that if the cylinder was going downhill that oil could run down there, past the rings and get into the combustion chamber. The advice above also, that one "tip" the bike to the right for a 5 seconds or so, is OK, but the oil available to run into the left cylinder probably drains for more than seconds, probably 15 minutes or so.

    Now...having said that, I STILL think that a person ought to do what he/she wants to do! I am not totally convinced (by the old timers who use this argument) that there is enough oil to matter anyway - getting into the left cylinder. Having said that it could happen, and probably does, is a different matter than saying that it happens enough to cause any problems.

    I personally, just like to keep my bike on the center stand.
    Last edited by jimmylee; 12-01-2013 at 06:02 PM.

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