The Flying Brick: 1985 BMW K100

This fun 1985 BMW K100 looks to be in shockingly good condition, thanks to long-term garage storage by the widow of the previous owner. These early K bikes were perhaps one of the purest forms of motorcycle made in recent memory, and this one’s low asking price of $3,150 or best offer seems like an awful lot of smiles-per-dollar. Find it here on craigslist in San Diego, California. 

The seller notes he purchased it from the widow of the second owner, who kept the K100 on blocks. The second owner / rider apparently cherished the bike, hence why his widow kept it under wraps for so many years. The bike looks all-there – the evenly-faded BMW roundel emblems indicate original panels and likely paint, and as a “naked” model with no fairing, it’s hard for this bike to hide any secrets.

Some may consider the K100 RS to be the more desirable specimen, especially since it came equipped with a fairing. Depending on your preferences, the fairing added some style and weather protection, along with adding some wind-cheating characteristics. This one sports low mileage, but the odometer seen here is a replacement. A little bit of quick trivia: these were called “The Flying Brick” due to the square shape of the engine case.

The current mileage is around 5,500, still quite low for the year. As seen here, the odometer was replaced by BMW, which would indicate to me that the original failed. If my vintage BMW cars are any indication, odometer failure is quite common, and it’s good to see the factory-authorized sticker here to establish provenance. These K100s are all the rage as naked bike bodies come back into style, and this one looks quite honest.

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Comments

  1. wuzjeepnowsaab

    These are great, under-rated Beemers. Never got the love they deserved buy they were well worthy of the marque…awesome performance and a style that would grow on you

  2. Wagon master Member

    I’m on it. LM cuz he’s in my area. I’ve had a woody for one for a while now. Hopefully he responds. Thanks BF!

  3. Dave Wright

    The reason these were unpopular is because they had an uncontrolled engine vibration that everyone hated. My busisness partner drove a 750 3 cylinder version for that reason. Only the 4 cylinders had it. I think they called it a “buzz”

    • Gerry

      Gee, I’ve owned and risen a 1985 k100rt for many many years and miles. Never found an “uncontrolled engine vibration.” Oh, I forgot, you never owned one. So your just making it up. OK.

      Like 3
      • Jerry

        Actually it’s very true that the K100 had a bit of buzzyness transferred to the bars. Most owners mitigated it by bar end weights. The 3 cylinder version is most definitely smoother as I can attest as I’ve owned one for
        over 30 years. Either way a good solid machine.

      • Preston R. Bergin

        Saved my life with Mitzler tires best bike I ever owned.80,000 CA miles. Next is a hover craft by Dave Wilcox no tires lil old brittle.

      • BobK

        Yes, I have only heard that these ran smooth as a watch, and I also have never ridden one. I just dream of owning one, and may some day if my wife lets me.

  4. Rock On Member

    Let us know how you make out Wagon master. How is that station wagon doing that you found On Barn Finds?

  5. Derek

    The brick engines make a decent transplant for Imps and variants, too.

  6. JohnD

    Good luck Wagon master. My dad had the K100LT, an ’86 I think, bought new. If they were under appreciated at the time it was news to me. They were well-respected tourers in their day.

  7. ROTAG999

    I owned a 93-4 there was a buzz thru the bars and in the summer if the cooling fan came on in traffic it was like a blast furnace not fun 750 is smoother and slower then one might think.

    Like 1
  8. Greg Member

    Great fun on these! I had a buddy in high school with one, and it was tons of fun for the dollar. My Mom currently has a 1200RS after selling her Harley, smooth as silk. Keep us posted Wagon Master!

  9. Bill

    My son had the 750. Very reliable and some common parts with 4 wheel BMWs. You could pickup lots of parts from NAPA!

    There always seems to be relatively low mileage 1000s and 750s out there for some reason.

  10. Dick Johnson

    Typical of Boomer odometer/speedos of the era, the sufferage of the same isn’t that bad on the Rs, but my riding buddy tells of high prices on the Ks. Still, you won’t see yourself coming and going. Neat bike.

  11. robj Member

    I had a K75 [750cc], actually a K75S and a K75RT. Both were the best bikes I’ve ever owned. One was for summer riding, [the S] and the RT for winter. Without a doubt the smoothest bikes I ever rode. It was like having an electric motor. That might not appeal to everyone but on road trips with 8-10 hour days it [they] was[were] perfect.
    My neighbor and riding buddy also had 2, a K100 RT and an S typeK100.

    On a road trip we swapped bikes. I was ready to swap back after 1/2 hour. The 100 had such a buzz to the bars that my right hand was falling asleep/pins and needles after 20 minutes. Couldn’t wait to give it back.

    Although not as common, find a K75, plenty of power and you’ll never regret it.
    Same bike, same frame, same everything, the engine was just 1 cylinder shorter.

  12. Jorge Garcia

    There was one of these for sale in my area last year for way under $1k. I did some research and found that the motors were manufactured by Renault. I checked a few YouTube videos on repair and maintenance and found that these bikes are not loved by the BMW enthusiast. I think it is way overpriced, now if this was an airhead that would be a different story.

    • Jonathan Q Higgins

      Jorge, the engines were NOT manufactured by Renault. But, later years of the bikes had pistons that were at least using a Renault design. The cylinders would seep a little oil into the combustion chamber if the bike sat for a while. You will notice that even on the side stand the bike is noticeably upright compared to other bikes. That was BMW’s early solution to the problem. I always put it on the center stand. There is a handy pull out handle to do so.

  13. Dan

    Great bikes, had a 1985 K100RT……..same color as this rode it everywhere on trips……smooth as silk….ah the good ole days…..

  14. Dick Johnson

    Tried numerous ‘fixes’ on buzzy bikes. Filling the bars with shot on my RTs and RSs, air grips in days of old, remount foot pegs, Shoo Goo inside pegs, you name it. Even tried drilling out foot peg mounting bolts. Gel sole inserts in my riding boots helped a little. Gel sole inserts in the crotch of your riding pants helps some on Harleys.

    Riding out of the buzz range is impractical on the super salb I didn’t seem to mind so much when I was younger. For the heat, I pull the lowers off the Rs during the warm months. Tired of baked ankles.

    Just why in the world BMW decided to put cylinders on the down side of the Ks while on a side stand is beyond me. SssssssMokin’! during a warm start.

  15. Rick Meisenzahl

    The K75s had the buzz and they lacked in sales, that’s why they stopped making them. The 3-cylinder was harder to run as smoothly as the K100 because the K100 had 4 cylinders and pistons counter-balanced each other.
    The dashboard is probably a re-built one because in 1985 the meters failed after only a few thousand miles. Some would conk out because they needed a new computer installed. After a lot of miles the engine would leave a small oil spot when left on the sidestand. Mine’s in the garage and since 1986 it has NEVER failed to start in the Spring on a single push on the starter.

  16. Will

    I’ve wanted the K75 flying brick for some time now, but this would do. Here’s the saved ad http://www.craigslistadsaver.com/view.php?name=BMWK-100

  17. Matt

    If my memory serves me correctly, the K75 engine had a balance shaft, and the K100 did not.

  18. leiniedude leiniedude Member

    ‘$3150 OBO. I’m motivated to sell.’ I do not follow prices on these but this seems like a great deal!

  19. Z1rider

    In the early 70’s BMW was exploring an opposed 4 to replace their flat twins. The release of the Goldwing by Honda shelved those plans. In fact BMW seriously considered getting out of the motorcycle business. Bob Lutz is at least partially credited for saving the motorcycle side of the business with the R series. The K series was BMWs answer to ever tightening emissions regs and the need to respond to the Japanese competitive threat.

    The K75s benefitted from a balancer which was easy to incorporate since it ran at crank speed, correct for the inherent imbalance a 3 cylinder. The four cylinder, as all inline 4’s develops secondary imbalance. Secondary refers to the frequency of the imbalance, or 2X. It would therefore require a balance shaft running at twice crank speed to be effective. BMW elected to skip the complexity and expense required for that.

    That’s why the 75 is smoother than the 100.

    • On and On On and On Member

      Hey thanks Z1rider, I learned something. I had a K75. Great bike, one of my favorite riding bikes. My buddies all rode Harleys and I said someone had to have a dependable bike to go fetch parts for your Harleys. True about the smoking on start ups. Disconcerting but harmless. A flat 4 BMW? That would have been cool……………Hey leiniedude, what town in YAHEYland do you live in?

      • leiniedude leiniedude Member

        Ya der hey On and On! I am thirty miles due South of the Mad City, on the Sugar River near the Village of Albany. Are you close enough to get together for a Leinenkugel and some stories? Take care!

      • leiniedude leiniedude Member

        Lol! I could have used your part pick up service years ago. E mail is sent Brother. Thanks! Mike.

  20. ROTAG999

    The early ones would puff smoke and was told that motor was upside down from what BMW planned but cost to change it would have been too much my 93 never smoked or used oil my 03/1150RT used oil but was told that it was designed that way being a oilhead always smart to check for fluids and air pressure everytime i ride now which is less then years gone by.

  21. Dick Johnson

    The 12 Benz engines on the BF 109 was inverted, and smoked less than some bikes’ maintenence maladies. Owner induced. Gold Wings can smoke with the best of them. My aging RT is always parked on the center stand to avoid embarrassment during hot starts. A small price to pay. . Especially for a bike with 156,700 miles on it.

    AIR HEADS FOREVER!!

    Like 1
    • Z1rider

      I have a vague recollection that later K bikes had pistons with pins in the ring lands (similar to a 2 stroke) to keep the ring gaps from migrating down to the low side of the cylinders. This was supposed to eliminate or at least reduce the smoke on startup.

  22. On and On On and On Member

    You bet leiniedude. I’m in Lodi, 20mi north of Madison. Know the Albany area well. Keep in touch, my email is durant28@yahoo.com

  23. JohnD

    Dad had the bar-end weights on his. I rode it once, and didn’t notice any buzzing, but then again, I was just holding on for dear life as I’d never ridden anything that big before. Dad never complained about buzzing, and trust me if the K was anything less than perfect in his eyes I would’ve heard about it.

  24. Mark S

    I’ve always like the r series more. I think the boxer with a shaft drive was the more reliable bike.i currently ride a 1977 gold wing with a custom sidecar, but I sure wouldn’t turn down a R1200RT which I would promptly install a Ural sidecar onto it.

  25. Peter Perfect

    Looking forward to picking mine up in a couple of weeks (as soon as my mechanic has the space..!) It’s a 1991 K75 RT and it’s been sitting on the guys front driveway for…, wait for it…, eight years..!!

  26. michael t kirwan

    picked up a 85 k100 cheap and got the wiring figured out and off we go. Fun machine . along with my harley( like riding an anchor in comparison)

  27. Tom Featherstone

    I bought my 85 K100RT new in the spring of 86, and I’ve never regretted it. After approximately 250,000 km, the rivets on the engine output shaft shock absorber failed and I pulled the engine apart last winter (2018) to rebuild it. Amazingly, there was virtually no wear on the engine, but I replaced the piston rings, engine seals, gaskets, cam chain and output shaft (with bearings). I also balanced the engine while I was in there, and the engine buzz is much improved. Bike runs like new, only better.

  28. Paul Bogdonoff

    I have one just like it, foam grips help but still got the buzz (unless you keep it over six grand) buy this bike you won’t regret it. The bike is bullet proof, keep it on the center stand or it will smoke. Big deal. This bike is smooth and balanced and has serious torque. My other bike is a Ducati 998 and is where I get my ya yahs on the track. The Beemer is altogether different and is home on any road, and won’t disappoint your when you drop it down and go. It won’t leave you stranded.

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