Airhead oil consumption Bulletin 1975

Discussion in 'Airheads' started by Hawk Medicine, May 4, 2012.

  1. Hawk Medicine

    Hawk Medicine Coyote's Brother

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    #1
  2. Cordless

    Cordless Two Wheel Addict

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    Very interesting.

    I was wondering why the dipstick on my '75 R90/6 has a second, lower, full line. This explains it.

    Thank you.

    Do you have any more of these Ah Ha tech bulletins?

    Should we start a thread with nothing but BMW Airhead Tech Bulletins? Does such a thing already exist and I know nothing about it?
    #2
  3. ignatz72

    ignatz72 call me iggy

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    Good to see this in writing, as I've trusted the common wisdom on this for a while now.

    Now if you could only find a similar doc decreeing what brand and grade of oil that should be used to not fill to the max line...

    But then there'd be one less thing to argue about here on rainy days.
    #3
  4. blaine.hale

    blaine.hale Long timer

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    At one point, I'd fill to the top line and noticed a lot of oil consumption. I finally settled on about 2.0 US qt (halfway between the 2 markers on the stick) and that oil consumption all but stopped completely.

    Wonderful to see my observation in writing there! Thanks for posting this.
    #4
  5. DoktorT

    DoktorT BigBrowedNeandereer

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    I heard of that bulletin back in the day, but had never actually seen it. I put 3 piece oil control rings on my 90/6. Check oil level at every gas tank fill until you learn your uses and adjust as knowledge develops. My 79 RS needs a top up every 2 tank fulls or so.
    #5
  6. aitepaeapaea

    aitepaeapaea n00b

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    ...to stuff, having put less than 1500 miles on my new-to-me bike. My instinct tells me that 2 liters of oil for a 1000cc (R100/7) engine is anemic. So I've tended to try to keep it pretty close to top. Now, that said, top, measured on the side stand rather than the right way, is maybe 1/8" or so above the 2 mark on the stick. The bottom line is that I seem to blow through about 1ml/mile. The oil isn't becoming especially discolored. From aircraft engines I'm cool with blowing off some oil. So I guess I'll keep on keeping on until I learn better... :wink:
    #6
  7. Bill Harris

    Bill Harris Confirmed Curmudgeon

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    From the quoted SB, this is going to get some infamous wrench upset.:eek1:eek1:lol3

    We've been saying and doing this for years:

    Although the SB was a CYA for the 1000cc warranty woes, it also applies to the 600 to 800 cc jobbies too.

    In my own bike, installing a deeper "3 Qt sump", lowering the oil level and using a longer "A" dipstick (MAX is 16mm lower), I minimized oil blowout thru the breather. A new reed-type of breather valve helped, too.

    --Bill
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  8. CptImagine

    CptImagine NCC-1701-B

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    IN my and my crews experience, they're all different and have a desired full level specific to that engine . New owners traditionally had the air box and plumbing on late models fouled with oil in no time . Carbon build up in the left cylinder is huge with sidestand users . That by keeping the crank case dipstick topped off . When the engine stops blowing oil thru it, that is the full mark on your dipstick/engine . Add more, the blowbye increases, along with additional pressure on an engine with 80-90 psi already . Then seals become an issue, due to habitual over filling and the increased pressure . My rt level is only 1/8" above the MIN mark . My gs with a Breil extender allows only 1.9 quarts total before blowbye kicks in mega big time . Pre Breil 1.45 quarts was the frightening max. on that engine .
    #8
  9. silverhead

    silverhead Been here awhile

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    "influences caused by the driver like acceleration and retardation"

    Is this a service bulletin or a lecture from a police officer? :)


    That is about where my oil level has settled to at the moment on my R90/6 and isn't moving. This is as a new airhead owner who has never had one before. I pretty much do this with all of my motorcycles: I change the oil when I get them and then ride them for a while.. Ride them hard a bit. Keep my eye on the oil level and see where it 'stays' and make a mental note. Almost every car or bike I've owned does the same thing if you overfill them and almost all of them are marked slightly incorrectly on the dipstick as to what 'full' is.

    On old bikes it'll mostly just burn off and I never notice it. On cars you can damage turbos and catalytic converters, so I do take note of the natural 'full' on everything I own.
    #9
  10. Uke

    Uke visualist

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    Any informed opinion if this bulletin applies to later bikes, or was the dip stick marks adjusted at the factory? The recommended volume for an oil and filter change for the '93 R100R (as per the Rider's Manual) is 2.5 litres.
    #10
  11. Bill Harris

    Bill Harris Confirmed Curmudgeon

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    Good question. It may or may not.

    Various oilpans (differing in depth) and oil dipsticks (differing in length) have have been utilized over the years.

    See Anton's page on this:

    http://largiader.com/tech/oilpan/ :huh

    --Bill
    #11
  12. silverhead

    silverhead Been here awhile

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    After attending a business meeting for work last week that left me in 'motorcycle parking' on a hill I had to use the side stand against my will. I have no idea how much oil got into the cylinder, but I could have cleared a city block of mosquitoes after I started it up!
    #12
  13. supershaft

    supershaft because I can

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    A BMW service bulletin makes it official? If only it were that simple since a lot of BMW service bulletins don't pan out in reality. This one is yet another. I have known of this bulletin since it first came out. I use to catalog all the service bulletins at the dealership I then worked at.

    To me the most dangerous aspect of this bulletin is that some readers might think that their oil level won't go any lower once it 'settles'. This can get you into trouble since I have seen many airheads run completely out of oil. It's not good. Seeing that happen adds up with my own experience. My R69S to my '92 R100 does not stop using oil somewhere in the middle of the dipstick. From what I can tell, when my bikes get down to the half way mark they use oil like they did before or more so. The one oil use pattern that I have seen over and over again is that my bikes tend to not use any oil after an oil change for some time. The oil level remains constant for some time and then it starts going down. Once that starts, I have never seen the level steady somewhere in the middle of the stick.

    I suspect oil usage does taper off as the level decreases for some. It never has for me. But I know for a fact that oil usage does not stop there for myself and others. I have seen a number of airheads and oilheads run completely out of oil.
    #13
  14. SculptD

    SculptD Smells like tech

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    This is a very good point. My R75 has always settled at the halfway mark as has been described. So, I assumed the R100 would do the same. Nope. It just keeps on dropping. The breather setup is completely different, among other things, so I shouldn't have made that assumption in the first place.
    #14
  15. ozmoses

    ozmoses ...

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    Odd; exactly my experience x3.

    So, can this be considered "normal" usage?
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  16. disston

    disston ShadeTreeExpert

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    My R90/6 uses oil all the time but it does seem to me to use it faster at the top of the dipstick. So I usually run it or fill it only half way up or just a bit more. Rarely fill it all the way.

    I find this SB very interesting. Glad there is more to the issue than rumor or Shadetree advice. :lol3
    #16
  17. Stan_R80/7

    Stan_R80/7 Beastly Gnarly

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    My oil usage agrees with SS and ozmoses. The oil level very slowly decreases over miles and time between the 'full' and 'add' marks until ~ 2k miles, then oil consumption increases. At that time, oil can be added or changed. Often, I change the oil at ~ 2k miles because consumption is then reset and it will consistently not use much oil for the next 2k miles (with or without a filter change).
    #17
  18. 190e

    190e Long timer

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    If a bike burns oil due to general wear there is no reason for it to stop at some particular oil level.

    The way I read that bulletin is that the combination of high oil level and high revs is too much of a challenge for the breather. That's different from burning oil due to wear and perhaps bikes that don't burn oil due to wear will consume oil if the level is too high but will cease to do so when the oil level is lower. There is another later bulletin which is less specific but infers the same problem. It reads as though it's aimed at relatively new bikes and warranty claims. They were trying to provide guidance that would eliminate the breather use of oil so that the owners didn't think they had a warranty claim due to a prematurely worn engine.
    #18
  19. silverhead

    silverhead Been here awhile

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    I've had vintage bikes that are in good shape that'll blow out a lot of oil if you run them down the highway hard but not use any if you just drive around town. Then I have other bikes like my TW200 that only have a 1qt capacity, but will handle 10k RPM for hours on end and not use a drop of oil even though it feels like you're beating them like a rented mule. I haven't figured out all the nuances of oil usage in my R90 yet because I've ridden it less than 1000 miles.

    But if the rings and guides and gaskets aren't sealed properly anything goes as to what will happen. My rings are barely in spec for gap, so it won't surprise me if my plugs blacken and I end up using oil slowly.

    I check my oil about once every week just out of habit from owning bikes that were known to blow it right out of the breathers. I check it by touching the unthreaded head of the dip stick to the engine case threads as opposed to screwing it in. That's correct, yes?
    #19
  20. disston

    disston ShadeTreeExpert

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    I have seen it described as related to the splash oiling. A higher oil level has more oil thrown around by the spinning crankshaft. More oil that gets on the rings. More oil on the rings means more oil gets by the rings.

    Some deep oil pans are set up to counteract the same issue. If the deep oil pan uses an extension on the pick up then the oil level can be lowered. Lower oil level has less oil being flung around by the crankshaft.
    #20