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Thread: Valve Adjustment

  1. #1
    Registered User pschuyler's Avatar
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    Valve Adjustment

    I just received my new BMW Owners manual for my R75.

    The valve adjustment measurements state .15 and .20 for intake/exhaust, which differs from Clymers. I'm assuming the BMW manual is correct, any input from the forum?
    Peter Schuyler

  2. #2
    Registered User lkchris's Avatar
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    Yeah, the information in the BMW manual came from BMW.

    As for Clymers, who knows?
    Kent Christensen
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    '12 R1200RT, '02 R1100S, '84 R80G/S

  3. #3
    Liaison 20774's Avatar
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    I'll guess that your Clymers says 0.10/0.15. The value settings have changed, even from BMW, over the years. The lastest service bulletin that I can find (ca 1984) set the clearances to 0.10/0.20 intake/exhaust after break-in. But the 0.15 for intake is a good thing to do. It doesn't detract noticeably from engine performance but does allow the valve to rest on the seat for a fraction of time longer, helping with heat transfer. The intake valve needs this less than the exhaust valve due to the in-rush of cooling air-gas mixture.
    Kurt -- Forum Liaison ---> Resources and Links Thread <---
    '78 R100/7 & '69 R69S & '52 R25/2
    mine-ineye-deatheah-pielayah-jooa-kalayus. oolah-minane-hay-meeriah-kal-oyus-algay-a-thaykin', buddy!

  4. #4
    #4869 DennisDarrow's Avatar
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    Not that I quote Paul Glaves as the end all of information; but he discusses valves in depth in the July issue of "The News". He is much more in touch with bulletins, etc than I will ever be..........on page 30, "The latest bulletin calls for all Airheads to be set at 0.15 intake and 0.20 exhaust".


    Thanks Paul........Dennis

  5. #5
    Registered User pschuyler's Avatar
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    BMW moa article

    Thanks that article was right under my nose the whole time.
    Peter Schuyler

  6. #6
    Manfred
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    FWIW, Snowbum's airhead top end manual says to set intake at 0.006 in and exhaust to 0.010 in.

  7. #7
    Liaison 20774's Avatar
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    Quote Originally Posted by Manfred View Post
    FWIW, Snowbum's airhead top end manual says to set intake at 0.006 in and exhaust to 0.010 in.
    That would be Oak's topend manual. The 0.010 seems a bit much and will result in a bit more noise. Probably OK but 0.008 works just fine. FWIW, Snowbum has discussed using 0.0085 for the exhaust. I think he does it like others have mentioned...0.009 won't go but 0.008 will slip through.
    Kurt -- Forum Liaison ---> Resources and Links Thread <---
    '78 R100/7 & '69 R69S & '52 R25/2
    mine-ineye-deatheah-pielayah-jooa-kalayus. oolah-minane-hay-meeriah-kal-oyus-algay-a-thaykin', buddy!

  8. #8
    rbleau
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    Did you get your answer ?

    Howdy Pete !

    Looks like you need to set em where you like !


  9. #9
    Registered User ebeeby's Avatar
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    Heck, I've always used .006 and .008 as I thought that was "correct" for an R75/5. Come to think of it, I can't recall where I got those specs.
    Old age sucks.
    1973 R75/5

  10. #10
    Beemerphan Radar41's Avatar
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    Thumbs up Airhead Valve settings

    Quote Originally Posted by ebeeby View Post
    Heck, I've always used .006 and .008 as I thought that was "correct" for an R75/5. Come to think of it, I can't recall where I got those specs.
    Old age sucks.
    According to my master tech. (he was a BMW mech in those days) .006 intake and .008 exhaust is correct for my 84 R100RS don't know about the others.
    Don "Radar" Wreyford
    00 K1200LT, 98 R1100GS AE, 84 R100RS, 76 R75/6
    MOA # 91738, RA #27032 , ABC #7915 - "Insanity is doing the same thing over and over again, but expecting different results" - Albert Einstein

  11. #11
    JAMESDUNN
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    Matt Parkhouse.

    Quote Originally Posted by DennisDarrow View Post
    Not that I quote Paul Glaves as the end all of information; but he discusses valves in depth in the July issue of "The News". He is much more in touch with bulletins, etc than I will ever be..........on page 30, "The latest bulletin calls for all Airheads to be set at 0.15 intake and 0.20 exhaust".


    Thanks Paul........Dennis
    Matt Parkhouse, "Keep 'em Flying", recently recommended this setting as I recall, not Paul Glaves. BMW recommends 0.10 mm for intake and 0.20 mm for exhaust, but as pointed out in post #3 by 20774 there are benefits to a "looser" intake setting. I use 0.15 mm intake and 0.20 mm exhaust ; a little more noise perhaps but I love the sound.

  12. #12
    #4869 DennisDarrow's Avatar
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    whoa......I am ever bad......MATT......sorry for getting the credit wrong.............one of those old ages moments I guess........But at least I was so impressed with the information from YOU that I remembered that..........God bless the old guys......Dennis

  13. #13
    Rally Rat
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    Valve Adjustment

    Cams are ground with acceleration and deceleration ramps on the lobes. The purpose of these ramps is to start lifting the lifter and valve gear slowly to overcome the inertia of the valve and valve gear as it begins to move and lift the valve off the seat. Then the lobe basically whacks the valve nearly to full lift and there is a ramp slowing the rate of lift as the valve reaches full open. This is to keep the valve gear from floating away from the cam and overlifting the valve, maybe tagging the piston. As the lobe begins to rotate out from under the lifter there is a ramp that starts the lifter slowly down, once it is moving the lobe drops off real fast and almost closes the valve. Now here it the point of this long winded post. The lifter gets to the deceleration ramp that slows the rate of drop (valve closing) and gently sets the valve down on the seat. If you arbitrarialy increase the valve clearance adjustment beyond what the engine/cam designers intended, the valve slams into the seat before the deceleration ramp is finished doing its job. This pounds the seat and valve and causes the adjustment to close up a lot faster than normal seat/valve wear. Going from .10 mm to .15 mm doesn'r seem like much, but it is a 50% increase in valve clearence.

  14. #14
    JAMESDUNN
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    0.15 mm vs. 0.10 setting for intakes.

    Quote from George R.:If you arbitrarialy increase the valve clearance adjustment beyond what the engine/cam designers intended, the valve slams into the seat before the deceleration ramp is finished doing its job. This pounds the seat and valve and causes the adjustment to close up a lot faster than normal seat/valve wear. Going from .10 mm to .15 mm doesn'r seem like much, but it is a 50% increase in valve clearence. ; unquote.

    Great post George and informative. But if so many "gurus" recommend the .15 vs. .10 have they not considered any ill effects? I have been using the .15 on intakes and detect no negative consequences as yet. Matt Parkhouse does say in the July "Keep 'em Flying" ,and I paraphrase, " You can use a tighter setting than the .15 intake if you so choose.", referring to the .10 gap, I suppose.

    Your thoughts pleas, as I really resp[ect Matt's opinions and advice.

  15. #15
    keelerb
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    Question

    An interesting debate. I use the .006/.008 clearances myself (saves memory, among other things, as my Commando uses the same settings), thinking that looser is better (more time to cool on the seat), although maybe not so important for the intake valves. I have an 84, so want to fend off the inevitable rebuild as long as I can.

    Will be interested in everyone's views/experiences.

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