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Thread: 84 airheads valve recession

  1. #1
    keelerb
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    84 airheads valve recession

    I was happy, if a bit dubious, to read Matt Parkhouse's article in the latest ON, in which he says that the infamous unleaded gas valve seat recession issues are mostly a pre-1984 issue. I thought the 84s were equally affected? As the owner of an 84 (no issues so far, but I keep a watch on it) I'd love to think this is true but it's not what I've always understood. Thanks - B

  2. #2
    Administrator 20774's Avatar
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    I haven't seen the newest issue yet, but I also thought the problem wasn't fixed until the 1985 models. In truth, the problem was not recession of the valve seat but rather deformation of the valve face itself due to poor heat transfer to the seat. The valve kept getting hotter and hotter and eventually tuliped and fell into the head.

    Oak Okleshen wrote a pretty definitive article in the March 2002 Airmail for the Airheads Beemer Club in which he describes the problems in great detail. He state many times that it is '81 thru '84 models.

    It's easy to mistype something as in '84 instead of '85 or forget to use the word "thru". We'll see how this all shakes out...
    Kurt -- Forum Administrator ---> Resources and Links Thread <---
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  3. #3
    keelerb
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    Thanks Kurt. That's my understanding too. I'll continue to monitor the situation and perhaps use a little ValvTect once in a while.... - B

  4. #4
    Friday Yet? 97077's Avatar
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    Valve recession

    I had to have a valve job on my 85 R80 RT at 70,000 miles. Why? I'm not sure. My 86 R80 made it all the way to 188,000 miles. My 88 R100RS made it to 126,000 miles. Why the difference between the 3 is a good question. Kevin

  5. #5
    Registered User beemerguru's Avatar
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    '81, '84,'88, '92...it really doesn't matter. Any year is subject to valve recession. If you need to constantly reset the valves every 3-5K miles, that's a sign.

    When you do a valve check,,,when you pull the valve covers, is the front of the head a golden brown or dark brown but the rear is still clear aluminum? That's a pretty good sign that somewhere in the past, the head was running very hot. Another reason to pull the head and have a look.

    I always pull the head when I get a bike in for rebuild. I'd say 85% of the time, at least the valve seats and/or guides need replacing.

    Got one with 15K original miles in right now for a complete rebuild..but it sat outside for 7 years. Ya never know.
    Greg Hutchinson
    R80G/S (4) 633CSi with 450K mile
    '68 R60/2 '88 K100RS Special Edition
    http://gregsgssite.shutterfly.com/

  6. #6
    Benchwrenching PGlaves's Avatar
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    OK - valve problem history primer:

    Starting in 1980 (US model year) BMW introduced new, very hard, no-need-for-lead, valve seats. But the R100 models particularly, and the R80 models too but to a lesser extent, started exhibiting the annoying need for very frequent valve adjustments. When taken apart the exhaust valve heads were found to be deformed, but the seats SEEMED perfect. Early on, shops replaced the damaged valves and left the seats. But often the problem just repeated itself.

    Then BMW determined that even though the valves were deforming it wasn't a problem with the valves really. The new hardened seat material was poor at conducting heat. Valve to seat contact is supposed to conduct heat away from the valve heads. But the poor heat conductivity of the seats caused the exhaust valve heads to overheat and deform. They physically curled at the edges allowing them to pull deeper into the seat - closed up valve gap.

    The real cure was to install the new 2nd generation of hardened seats which did conduct heat sufficiently to cool the valves normally. The second new seat material was introduced in the production of the '85 models.

    This valve head deformation common on the 80 through 84 models is not true "valve recession" in a technical sense. Valve recession is technically the receding of the valve head deeper, and ever deeper into the valve seat as the seat material wears away. And this is typically found on pre-1980 models where the seat material was intended to be lubricated by the tetraethyl lead used in gasoline. The original hard seats were to combat the lack of lead, but the "law of unintended consequences" caught up with BMW due to the heat transfer issue.

    1985 and later models do not exhibit severe problems of either type - but they do exhibit normal valve head and seat wear over time - usually a long time (in miles).
    Paul Glaves - "Big Bend", Texas U.S.A
    "The greatest challenge to any thinker is stating the problem in a way that will allow a solution." - Bertrand Russell
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  7. #7
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    This is also my understanding. And, it can happen to R65/R45 bikes as well, though they are a bit less prone to it as there is a bit less thermal energy produced in the smaller displacement engines. But it still does occur, and the short-stroke motors use smaller diameter valve stems, so the valve head heating can in theory be more critical with detaching the head from the stem on these bikes. I watch my valve lash adjustments closely, and also tend to run the clearances on the generous side of the spec, to give a bit more contact time with the valve seat, cross my fingers, and don't run the air/fuel mixture too lean.
    BMWs in my garage: 1982 R65LS, 1978 R100/7

  8. #8
    sumran
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    Quote Originally Posted by PGlaves View Post
    OK - valve problem history primer:

    Starting in 1980 (US model year) BMW introduced new, very hard, no-need-for-lead, valve seats.
    Thanks for the good information. Mine is a 1980 model, but it has a manufacturing date of April. I am under the impression that my heads are like the '79 rather than the '81, but I may be incorrect. Do you know if the early '80 bikes had the new valve seat material?

  9. #9
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    I *think* the confusion can come from the fact that BMW's production line shuts down for the month of August, and when they start up again sometime in September, they are building the NEXT model year's bikes, so the 1981 models first started production in Sept 1980.

    I think that the valve seats change was simultaneous with the Nikasil cylinder liner, which went with the 1981 model year bikes (that also had the lighter clutch/carrier assembly).
    BMWs in my garage: 1982 R65LS, 1978 R100/7

  10. #10
    Registered User lkchris's Avatar
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    Here's what ruined exhaust valves from my '84 R100RS look like.

    At about 50-60K miles.

    Recall that a portion of this has to do with the fact the R100 heads through '84 were the "big valve" heads matched to 40mm carbs and those installed later (and '77-'78 R100/7) had smaller valves and were fitted with 32mm carbs. That is, there was less actual head material to absorb heat and the heads themselves are not as reliable as those with smaller valves.
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    Kent Christensen
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    '12 R1200RT, '02 R1100S, '84 R80G/S

  11. #11
    Rally Rat
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    Valve recession

    Paul's post was as usual, right on the money, except for one thing. The latest seats were installed for the model year 1986.

  12. #12
    Benchwrenching PGlaves's Avatar
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    Quote Originally Posted by lostboy View Post
    Paul's post was as usual, right on the money, except for one thing. The latest seats were installed for the model year 1986.
    I stand corrected - thank you. The important point and it is still very important as fewer techs remember the issue. That point is:

    Even if the seats look pristine, when the valve heads are deformed - you must replace not only the deformed valves but also those great looking seats or the problem will just happen again.
    Paul Glaves - "Big Bend", Texas U.S.A
    "The greatest challenge to any thinker is stating the problem in a way that will allow a solution." - Bertrand Russell
    http://www.bigbend.net/users/glaves

  13. #13
    Registered User PHMARVIN's Avatar
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    Hi, All,
    If the original poster's question was, "Are the 1984 models affected by the so-called valve recession problem," the answer is a resounding YES. My late wife, Harriet, owned the next-to-the-last dual shock USA spec R100RS, a 1984 model (built in September, 1984), serial number 6227336. The valves and valve seats needed to be replaced due to the valve seat problem at 64k miles.
    Ride Safe,
    Phil Marvin - El Paso, TX
    '94 K75A/3
    '95 K75RTP

  14. #14
    Administrator 20774's Avatar
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    Valve Seat/Valve Problems '81-'86??

    Note...I really meant to say '81-'85 on the post title...

    Where is the information that indicates the problems extended all the way through the 1985 models? Everything I've ever seen, by many experienced mechanics/owners/gurus, has indicated that the problem was really through 1984. This whole thread started with a comment on Matt's latest ON article where he states that it was through 1983. How could that have gotten through review if the new "end date" is now 1985? Matt's comments for '83 was the first I'd ever heard that early...now it's 1985? There seems to be too much disagreement in this...over such a wide period...
    Last edited by 20774; 10-18-2008 at 06:09 PM. Reason: Changed end year...
    Kurt -- Forum Administrator ---> 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!

  15. #15
    Registered User lkchris's Avatar
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    Yer gonna find "1985" Airheads pretty rare.

    Perhaps just some R80RTs is all you'll find.

    No R100s between 1985-1987.
    Kent Christensen
    21482
    '12 R1200RT, '02 R1100S, '84 R80G/S

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