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Thread: Engine differences on K100's from 1986 thru 1988 ?? 2-valve engines only

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    Engine differences on K100's from 1986 thru 1988 ?? 2-valve engines only

    Are the engines (2-valve models only) on the K100's from 1986 thru 1988 pretty much the same??

    I am sure there were some upgrades/design improvements. Can any one elaborate on these differences? How many of the parts of an '86 K100RS would be usable on an '87 K100RS?? What definitely NOT be the same?

    Thanks in advance.
    "The difference between death and taxes is that death doesn't change every time congress meets." - Will Rogers

  2. #2
    Benchwrenching PGlaves's Avatar
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    This taxes my memory but my recollecion is that the significant changes were between the 83-85 models and the 86-later models. I think the camshafts changed between 85 and 86, and compression was reduced for 86. I am not aware of any significant differences after '86 until they came out with the 4 valve per cylinder motor. I was more tuned in to the K75s in that time period but don't recall significant changes to the 1000cc motor.
    Paul Glaves - "Big Bend", Texas U.S.A
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    Registered User lkchris's Avatar
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    Weren't there 49-state models plus California models originally?

    Then, they were all 50-state models.

    Probably repressing these memories.
    Kent Christensen
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    '12 R1200RT, '02 R1100S, '84 R80G/S

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    Quote Originally Posted by PGlaves View Post
    This taxes my memory but my recollecion is that the significant changes were between the 83-85 models and the 86-later models. I think the camshafts changed between 85 and 86, and compression was reduced for 86. I am not aware of any significant differences after '86 until they came out with the 4 valve per cylinder motor. I was more tuned in to the K75s in that time period but don't recall significant changes to the 1000cc motor.
    Thank you!

    A fellow across town has an '86 K100RS engine he wants to sell me. My son has an '87 that is pretty much pristine and runs great. I thought maybe someday there may be some parts that could be used that would be much cheaper than buying new or used when the failure happens. I have heard of problems with the gearing on the output drive shaft inside the motor.
    "The difference between death and taxes is that death doesn't change every time congress meets." - Will Rogers

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    A bozo on the bus deilenberger's Avatar
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    Quote Originally Posted by jimmylee View Post
    Thank you!

    A fellow across town has an '86 K100RS engine he wants to sell me. My son has an '87 that is pretty much pristine and runs great. I thought maybe someday there may be some parts that could be used that would be much cheaper than buying new or used when the failure happens. I have heard of problems with the gearing on the output drive shaft inside the motor.
    Well - we do have a current thread about the problem with the gear mounting rivets.. but that is REALLY rare. I had a spare engine for my '85 for most of the time I owned it. Bought it for $125 - with 3,000 miles on it. Finally got tired of tripping over it in the garage and sold it to a local mechanic, who got tired after a few years of tripping over it, and he sold it to someone else. AFAIK - it's in the corner of someone's garage today - just waiting for one of the worlds most reliable motors to blow up.

    If you get it cheap enough (less than $300) - it will invoke Eilenberger's Law of Spare Parts - "You never need what you have" (the K100 engine inspired that law..)
    Don Eilenberger http://www.eilenberger.net
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    Debbie's Servant Lee's Avatar
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    Quote Originally Posted by deilenberger View Post
    If you get it cheap enough (less than $300) - it will invoke Eilenberger's Law of Spare Parts - "You never need what you have" (the K100 engine inspired that law..)
    I agree. A spare Brick engine will most likely only be used as a door stop.
    Lee 2011 K1300S
    MOA # 30878
    Past BMW Bikes, 2003 K1200RS, 1991 K75S, 1987 K75T, 1984 R100RT

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    Quote Originally Posted by Lee View Post
    I agree. A spare Brick engine will most likely only be used as a door stop.
    Thanks guys!

    He never hot-rods it, and it runs perfectly, no oil burn, no missing, just solid. As an airhead loyal, I keep fearing his K bike will sometime fail (or is it, maybe I am hoping that it fail?). He keeps telling me that I need to get a K-bike, and I keep telling him that only "real" motorcycles for "real" men were the airheads!
    "The difference between death and taxes is that death doesn't change every time congress meets." - Will Rogers

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    Quote Originally Posted by jimmylee View Post
    Are the engines (2-valve models only) on the K100's from 1986 thru 1988 pretty much the same??

    I am sure there were some upgrades/design improvements. Can any one elaborate on these differences? How many of the parts of an '86 K100RS would be usable on an '87 K100RS?? What definitely NOT be the same?

    Thanks in advance.
    I replaced my 1987 engine with a motor from a 1988. No problems.
    My 1987 out put shaft rivets let go at 265,000 miles.
    It was cheaper to replace the engine than replace the shaft.
    Tim

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    The K-brick motor is probably the strongest link in the chain of those bikes, and would be the last thing i would expect to see fail.
    Ride Safe, Ride Lots

  10. #10
    Registered User beemerguru's Avatar
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    The 85 had euro cam but the rest of the engine was pretty much the same. If someone wants to build and engine, I have a completely rebuilt late model 2v head with Euro cams ready to bolt on.
    Greg Hutchinson
    R80G/S (4) 633CSi with 450K mile
    '68 R60/2 '88 K100RS Special Edition
    http://gregsgssite.shutterfly.com/

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