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Thread: Possible 85 K100 purchase

  1. #16
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    Quote Originally Posted by romulanremus View Post
    Well, he's had it since late 1984 from new, so I suspect that's got a lot to do with it. Who thinks they're going to keep a vehicle long enough for it to gain antique status? It's like the 69 Fastback Mustang I bought for $600 back in the 70s, bone stock with a 250-6 and a 3-speed manual transmission. I proceeded to try to turn it into a Boss-lookalike, V-8, 4-speed top-loader, fold-down rear seat, shaker hood etc etc. I'd love to have that one back just as I bought it, OEM hubcaps and all! Time's perspective, right?
    All the more reason to keep the original fairing and bags. These bikes are only original once, right down to the paint. When it comes to motorcycles, I'm a purist i guess, and hate to see bikes slip away piece by piece. Just a different point of view i suppose. My 1977 Yamaha xt500d is still original, not many xt's are anymore, and so are my airheads. To each their own. Good searching.
    Last edited by chunk; 10-27-2019 at 12:13 AM.

  2. #17
    Amateur Surgeon romulanremus's Avatar
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    I'm of a similar mind, Chunk. I'm not a fan of the cafe racer set, but whatever boats one's float. I'm putting a 1976 GL1000 back to original, since only 2000 of them were brought to the US. Others have been stripped down for cafe projects, sadly. I'm already prowling ebay for fairing bits and bags for the K bike, but won't pull the trigger till I go look at the actual scoot in Albuquerque.
    1997 BMW R1100RT
    1976 Honda GL1000 x2
    1981 Honda CB750C
    1974 Yamaha GT80

  3. #18
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    I'll throw in my two cents.
    In the 1990s I had my first new BMW, which happened to be an oilhead like you are riding. I missed the wrenching I had been doing on older bikes, so I bought a 1985 K100RS that needed some love. Before it was over, I'd sold the R1100 and have been riding Ks ever since.
    What I remember of that first K includes the unique seat which makes the passenger handholds a joke. My SO refused to ride on it until I swapped out the seat and tail for a later model's.
    The fuel tank mount is a poor design with support at the front, and a flat plate that extends from the rear. The weight of the fuel acts thru the tanks center of gravity (middle of the tank) which is unsupported. This tends to bend the rear mounting plate upward which can cause cracks where the plate is welded to the tank. Good luck finding a welder wanting to weld fuel-soaked aluminum.
    The early Ks were buzzy. BMW spend the entire product run trying to minimum the vibes by mounting all the touch points in rubber. You may find certain RPM ranges to be unpleasant.
    The instrument pods were notoriously unreliable. They were often replaced and/or recalled. Don't necessarily believe what the odo reads.
    The brakes squeal. The calipers and rotors are all hard mounted, unlike more modern floating designs. You can play with anti-squeak compound on the pads, or just learn to ignore the squeal. And while vastly better than the drums that preceded them, they don't stop as well as later multi-piston designs.
    Overall I'd rate them a good, solid, basic bike. They obviously clicked with me, primarily because of the wide, easy to use powerband. If it clicks with you, go for it. I'd dismiss any thoughts of it appreciating as a collector's item.

  4. #19
    Amateur Surgeon romulanremus's Avatar
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    I appreciate the thoughts. I have an 81 CB750 that I chased vibes on for months before finding out it’s inherent in the side-by-side 4-banger design. So sort of used to the buzz; I even halfway named the thing “Buzz Boy Blue”. And most everything I buy to ride are from the 70s or 80s, so not nervous about this one. And the only thing I’ve had long enough to appreciate in value, I married 34 years ago.
    1997 BMW R1100RT
    1976 Honda GL1000 x2
    1981 Honda CB750C
    1974 Yamaha GT80

  5. #20
    Registered User Rinty's Avatar
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    Quote Originally Posted by romulanremus View Post
    I have an 81 CB750 that I chased vibes on for months before finding out it’s inherent in the side-by-side 4-banger design..
    What I've read is that, with an in line 4, the outer pistons go up and down together, the inner pistons go up and down together at a 180 degree interval from the outers, so all four hit "half" mast at the same time, when their respective con rods are at maximum deflection from the vertical, which causes the vibration. Thus, the need for counterbalancers or double counterbalancers.

    I rode a K100RS once, and found it quite buzzy below 4,000 rpm, but don't know what year it was.
    Last edited by Rinty; 10-28-2019 at 02:53 PM.
    Rinty

  6. #21
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    As I said, I was riding a new R1100RS when I bought my first K, an 85 RS. I found the vibrations of a higher frequency than you get from oilheads, but the twins seem to have a greater amplitude. The vibes didn't seem that bad to me, but then I bought a K1100, which has much more rubber mounting (pegs and grips). A definite improvement. Then I went and bought a K1200 (rubber mounted engine). Smooooooooth!

  7. #22
    Amateur Surgeon romulanremus's Avatar
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    Quote Originally Posted by JeffDiCarlo View Post
    As I said, I was riding a new R1100RS when I bought my first K, an 85 RS. I found the vibrations of a higher frequency than you get from oilheads, but the twins seem to have a greater amplitude. The vibes didn't seem that bad to me, but then I bought a K1100, which has much more rubber mounting (pegs and grips). A definite improvement. Then I went and bought a K1200 (rubber mounted engine). Smooooooooth!
    That's the case with the CB line, also. The 750 is hard-mounted to the frame and uses a chain for the final drive. The 900, 1000, and I believe the 1100F all went to rubber mount points and shaft drive, offering a much less buzzy ride. I toyed with the idea of adapting rubber mounts from a 900 to fit the 750, but it would be much smarter just to get a 900, come to that.

    I'm hoping to get to look at the K later this week and see what it's like in person. I watched Chris Harris's video on prebuy inspections for K75s and K100s, and also the video on swapping out the final drive. Good stuff.
    1997 BMW R1100RT
    1976 Honda GL1000 x2
    1981 Honda CB750C
    1974 Yamaha GT80

  8. #23
    3 Red Bricks
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    Richard,

    If you want smooth get a K75. Nothing is rubber mounted. No need to. Smoothest running engine BMW ever built.

    Not quite the power (20-25 less) but plenty quick one up. The K75S is a lot of fun.




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