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Thread: 1987 K75S, tight valve.

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  1. #1
    Happily Bent dieselyoda's Avatar
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    1987 K75S, tight valve.

    I'm doing some long needed TLC to a 1987 K75S with 67,000 miles that includes a good tune-up. Since it's bucket and shims for the valves, I thought a thorough check of clearances was all that was required.

    The specs I have for intake clearances is 0.006" to 0.008", a universal intake dimension. Bear with me, I am now comfortable the specs are accurate. I use a 0.006" feeler gauge as my "Go" and the 0.008" as my "no Go"

    I get to #1 intake and I'm a "no Go" at 0.006". I'm a "Go" at 0.003" but close to a "no Go" at 0.004" and definitely 0.005" won't go.

    This is the intake so I doubt I've got a cupped valve, compression and leak down were great. I'm now concerned I have a pulled stem.

    The question: Do I change the shim to gain clearance or do I assume I have a pulled stem?

    Next question: Do these engines drop valves?

    There are some engines I'd be yanking the head and replacing all the valves if I saw this because I know they drop valves. Camshaft lobes don't grow. Add a moderate amount of wear to the camshaft lobe, maybe 0.001" max without case harden break through, I'm thinking this engine is necking the stem by 0.002".

    I feel like I'm gambling with this one and the only place I gamble is Vegas and I know I will loose there most of the time. I don't want to gamble on this one.

    Then again, I might be the only person that ever checked and it's been like that from the assembly line...........

    Thoughts? They are very much appreciated.
    1997 R1100RT (Restored Basket Case) , 1981 KZ 440 LTD (Restored Basket Case)
    1986 K75S(the beutch), 1993 K1100RS (blown engine), 1997 Chev Short Box (4x4 with an LT1)
    "You can easily judge the character of a man by how he treats those who can do nothing for him."

  2. #2
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    Change the shim. It is not uncommon for the intakes to tighten a little, however the exhausts have tightened more often on my 91 75RT. I would do all the valves and run it for 5000 miles or so and recheck.
    Ron

    91 K75RT ABS

  3. #3
    Registered User lkraus's Avatar
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    Not a problem, change the shim. Valves and valve seats do wear with normal use causing the clearance to decrease.
    Larry
    2006 R1200RT

  4. #4
    Mars needs women! 35634's Avatar
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    these engines rarely drop valves. They need so little care owners usually neglect checking them for 50k miles and then they might burn a tight exhaust valve.
    1987 K75S
    Original litter
    Original owner
    2012 Ural Gear Up

  5. #5
    3 Red Bricks
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    Yoda,


    It is kind of unusual to have an intake tighten up that much without the exhausts moving. Maybe the last person that was in there made a mistake in calculating the shim, went the wrong way, and didn't double check after the new shim was in.

    Since it is YOUR first time inside this particular bike, I would reset them so that YOU are sure that they are correct and see where things go in about 5k miles. Have not heard of any K75s dropping valves. I wouldn't worry.

    Shims come in approx. 002" (.05mm) increments.

    If you don't already have the shim tools or don't want to spring for the more expensive ones because you don't anticipate using them much, there used to be a guy that was making them. Don't know if he is still making them. You'd need to call or email him first to check. The quality was good for keeping a couple of bikes in shape for their life time. If you were going to make your living doing valve adjustments, you'd want the better ones. Kind of a Snap-on vs Harbor Freight kinda deal.

    Here's my comunication with him from 6 years ago:

    Hi Lee
    Yes, I have BMW "K" engine Valve Adj tools available for the 2 valve "K" engine.
    The 2 Pieces are made from 3/16? Laser cut steel. Working contours are identical to factory tools. Tools are new. Tools come w/ instruction sheet.
    $27 S/H included.
    Clutch pilots for K's are available also. New, from steel
    $18 S/H included.
    ?Pay Pal? to Polepenhollow, Cashiers Checks, Money Orders and Personal Checks accepted.
    I ship as soon as Pay Pal is posted or the check arrives.

    Thanks, Good Luck and Good Riding.
    Kenneth Lively
    318 S Hart St
    Palatine Il 60067

    polepenhollow@yahoo.com
    847-561-8555




    LONG MAY YOUR BRICK FLY!

    Ride Safe, Ride Far, Ride Often

    Lee Fulton Forum Moderator
    3 Marakesh Red K75Ss
    Mine, Hers, Spare

  6. #6
    Benchwrenching PGlaves's Avatar
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    I agree you need to get to a known base line. Without knowing the service history of the bike it is hard to tell what might be going on. My first K75 got one shim at 600 miles, and needed another (different valve) at 60K miles, then a third at 100K or so. It is possible that the seat moved a little and the valve hasn't been checked since that happened. In theory this settling in is all supposed to happen before the 600 mile service but; 1) it doesn't always happen that way, and 2) some frugal buyers neglect routine services.
    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

  7. #7
    Happily Bent dieselyoda's Avatar
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    Thanks for the advice, I'm going to take it and run

    Bringing the valve clearances to a known good value and running awhile makes sense.

    Tight intake valves on most engines would make me nervous but if dropping valves on this engine isn't likely, a few thousand miles should tell me if I have a problem. That might be entire season on this bike.
    1997 R1100RT (Restored Basket Case) , 1981 KZ 440 LTD (Restored Basket Case)
    1986 K75S(the beutch), 1993 K1100RS (blown engine), 1997 Chev Short Box (4x4 with an LT1)
    "You can easily judge the character of a man by how he treats those who can do nothing for him."

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