Airhead Valve Question

Discussion in 'Airheads' started by lloydunknown, Mar 20, 2011.

  1. lloydunknown

    lloydunknown Adventurer

    Joined:
    Mar 20, 2011
    Oddometer:
    78
    Greetings,

    I recently acquired an '83 r100rt. It is in pretty rough shape cosmetically, but seems to pretty average mechanically.

    I think I am experiencing the dreaded valve recession. Here's what I got:

    36,565 Miles:
    Left Intake okay at 0.10mm
    Left Exhaust okay at 0.20mm
    Right Intake NOT okay at 0.05mm reset to 0.10mm
    Right Exhaust NOT okay at 0.10mm reset to 0.23mm

    37,839 Miles:
    Left Intake okay at 0.10mm
    Left Exhaust NOT okay at 0.178mm reset to 0.229mm
    Right Intake okay at 0.10mm
    Right Exhaust NOT okay at 0.178mm reset to 0.229mm

    Thats 1,274 miles and 0.022mm movement on the left and 0.052 on the right.

    Thoughts? The PO told me that the bike probably has 50,000+ miles on it and that the odo does not represent the true mileage. Also, the title does not have an odo disclosure on it. It looks like it has seen high mileage. For example, the rear disc is almost worn out.

    Ideas?

    Thanks,
    Lloyd
    #1
  2. Dolly Sod

    Dolly Sod I want to do right, but not right now

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    I think a few more data points are needed. Ride it another 1000 miles and see what's up.

    How long did the bike sit before you picked it up?

    and change that rear brake pad.
    #2
  3. Solo Lobo

    Solo Lobo airhead or nothing

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    Well, the creep you see could be measurement error, and it small enough wouldn't do anything now but ride and continue to measure.

    Some will say that is the soft valve seats wearing, but I would say to wait until you need to replace them before making a change. I believe Airhead Wrangler saw some similar number on his ST, and then rode 15K miles to somewhere in South America and back from Seattle with no issues.

    How's the compression?
    #3
  4. lloydunknown

    lloydunknown Adventurer

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    Thanks, I'll ride it and get another data point. I had adjusted the valves before and not written down the info. I'll do that from now on.

    The bike had been a daily driver before I bought it.

    It has a very sad history. I think someone bought it new in '83 and let it sit forever. The logs I have on it show it had low mileage around 2004 and was well cared for. Well, except for the PPPO buying mirrors every year from knocking it over.

    Then it was sold to the PPO who kept no records. I imagine it was wrecked under his ownership since now the paint is not original or matching. Also, the fairing is tweaked and the valve covers ground up.

    The PO rode it as a beater for daily use. Now I'm the O.

    This would have been a great bike if the PPO didn't hose it all up.

    This is certainly a poorman's BMW. I can't afford head work so I really, really hope it is okay.

    Anyone know a good cheap source for a rear brake disk?
    #4
  5. squiffynimrod

    squiffynimrod maximum shrinkage

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    #5
  6. supershaft

    supershaft because I can

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    Did you torque the heads?
    #6
  7. Wirespokes

    Wirespokes Beemerholics Anonymous

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    Please fill out your profile so we can see where you're from. It'll help us answer some of your questions as well.

    Valve recession is due to the seats being too hard, not too soft. And normally if they're changing slightly it's not a big deal. With your larger gap of .008" they should do fine.

    But, if they're not, and they keep receeding at .oo4 or .oo5" a thousand, then it's probably time to consider replacing or repairing the heads. Don't push it, or run it hard in hot weather and you'll do fine till you've saved up the cash to renew or replace.

    It's been speculated that broken valves could be the result of worn valve guides, so keep that in mind.
    #7
  8. lloydunknown

    lloydunknown Adventurer

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    Thank you all for the prompt responses.

    "Please fill out your profile so we can see where you're from."
    I am in Delaware, USA.

    I'll keep an eye on the valves. I've been nursing a weeping fork seal since last summer. Today I noticed the leaking is accelerated and in danger of fouling the brake surfaces. I won't be riding until I replace those fork seals.

    Luckily, I have all of the parts in the garage and the oil.
    #8
  9. lloydunknown

    lloydunknown Adventurer

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    "Did you torque the heads?"
    I've torqued the heads at two valve adjustments so far. I don't have the numbers from those adjustments because I didn't think to write it down.

    I heard that you shouldn't torque the heads at every adjustment in fear of pulling a stud through the case. The last two times I did not torque the heads.
    #9
  10. Myro

    Myro Alberta Oilhead

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    Fort Saskatchewan, AB
    Personal experience, 82 R100RT, mileage at approx 40K miles. Valves needed adjustment every 600 miles. Pulled heads to rebuild and discovered that the seats were perfect but the valves were toast, almost ready to pull through the seat they were so thin and curled. Sorry it was a long time ago so have no pictures. The valves were poor quality metal and so was the final drive spline. This is apparently a known issue with this vintage of Beemers.
    #10
  11. fishkens

    fishkens Long timer

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    You can pull the spark plugs and rotate the engine to view part of the exhaust valves (use a flashlight) to check their condition.
    #11
  12. kraut.burner

    kraut.burner "Fun Club" President

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    Kind of abstract, but could there be a chance that it might be bad tappet adjusting bolts?

    I had ones that were stripped and kept throwing the valves out of adjustment. I'd usually end up with measurements similar to yours.
    #12
  13. supershaft

    supershaft because I can

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    Once I have checked the torque properly, I just check the torque versus re-torquing them. In other words, I don't loosen the nuts and then re-tighten. No need to really and I think it puts unneeded wear and tear on the components. Once a year or so is enough IMO but now you know that you do not have a stud pulling.

    Sometimes the seats are too hard and the valve gives and sometimes it is the seat that gives. Very often it is a combination of both.
    #13
  14. bmwloco

    bmwloco Long timer

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    Elaine (Vech's SO/Wife/Partner) has her own web page on how to adjust /2 valves. You can find it here:

    http://benchmarkworks.com

    No direct link as they have finally updated their web site! Look under "Tech Advice" on the left and then "Technical and How To". There is a wealth of knowledge and information there.
    #14
  15. danedg

    danedg Horizontally Opposed

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    How timely.
    I adjusted my /2 R60 valves last nite.
    Probably for the first time in 8 - 9000 miles.
    In the first 10K after rebuild, I checked 'em every 500 - 1000m, and gave up after 12K, cause they hadn't budged.
    Didn't check 'em at all last year. Another 8000 miles. Bike ran fine. There is one little tap, however.
    So, being completely bored, I pulled covers yester, and whipped out the feelers. Guess what?
    Dead on, both sides.:clap
    Then I read this thread, and went back to Elaine's Tech Article.
    I'd been doing right all along, but didn't realize that a push rod could be bent...and that might be the source of the unidentified tappety tap...
    How badly could the rod be bent and still operate? And if it IS bent, how long will it continue to operate in that condition?:ear
    Another 68,000 miles?:evil
    #15
  16. lloydunknown

    lloydunknown Adventurer

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    Thanks to all. I didn't expect so many replies. Currently, the bike is apart for fork work. Also, we're slated to get some snow at the end of the week. It should be a few days before I'm back on the road.
    #16
  17. Lornce

    Lornce Lost In Place

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    Lloyd,

    '81 - '84 airheads had valve seat material that was too hard for it's own good.

    Your exhaust valves are probably toast or on their way to being toasted. Your exhaust guides are probably shot, too. They're usually shot before 60k miles rolls around.

    If you want to save some money, just have your guides and exhaust valves replaced and count on doing it again every 60k miles.

    If you want to spend a wad, have your seats replaced too. If you're fortunate and it's done correctly, you won't have to worry about it again for a very long time.

    Take heart, you're not alone: This is an historical and well documented issue with 1000cc airheads mfg'd between '81 and '84.

    cheers,
    Lornce
    #17
  18. supershaft

    supershaft because I can

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    Every 60k miles? I thought that was the magic number for transmissions? Anyway, I think it all depends. Even for '81 to '84 models. Yes, a lot of them do have valve issues before their time but some don't. Other model years have valve issues before their time as well but not in such large numbers. Personally, I have seen a lot of exhaust guides with around 60k miles that could definitely stand to be replaced while you are in there but they usually aren't shot although I HAVE seen it. IMO, it's rare that you take some heads off with any kind of miles that still have perfect exhaust guides. I wore out a set in 60k miles in my LS but those heads warped beyond usage in another 25k miles. I don't think that is common but, still, I wouldn't have called the guides completely shot. My current ride's heads and guides are doing fine at 100k miles. I plan on fixing them when they need it. That could have been 60k miles ago or another 60k in the future. Who knows?
    #18
  19. Lornce

    Lornce Lost In Place

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    Lloyd,

    As evidenced by the rapid change in clearance, your exhaust valves are shot. It's the seat face of the valve that's giving up from the hot pummeling it's taking from too-hard exhaust seats. I bet you a doughnut your exhaust guides are finished, too.

    Valve guides are a whole $10 for the good aftermarket pieces from CC Products. :huh

    If you're going to take it all apart to change the exhaust valves, I wouldn't mess around with it. I'd change the exhaust guides, too. :deal

    Your intakes, valves and guides, are probably fine. They run nice and cool and properly adjusted last 4-ever. Almost. :evil
    #19
  20. supershaft

    supershaft because I can

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    Those CC Product's guides are great IF they don't come brand new with a ID that is already half way to worn out. Overall fit wise, I think you might be better with BMW guides. Personally, I would install CC Product guides undersized and Sunnen hone them to fit. I would machine a sharper oil scraper on them too. I think it does make a difference.

    I have seen those seats get hammered PLENTY of times. I would most likely change the exhaust guides too but I wouldn't change them at 60k miles just because.
    #20