BMW R100 Scrambler by Fuel Bespoke Motorcycles

BMW R100
BMW’s R series is seriously challenging the Honda CB as the custom platform of choice; over the past few months, a remarkable number of stylish 70s BMW customs have been popping up in the Bike EXIF inbox. This one was built by Karles Vives of Barcelona, Spain, and it’s an RT model—which in BMW’s complicated lexicon, means it’s a tourer. (This was best explained by Cycle magazine’s April 1979 test: “The new RT can best be described as a full-house touring version of the RS, which is a semi-touring version of the S, which is a sporting version of the pipe rack R100T, which is a bunged-out version of the R80/7. Which is a slightly overbored and subtly refined update on the discontinued 750cc model.”) The RT was also the most expensive motorcycle in the world in the late 70s, surpassing even Harley-Davidson’s Electra Glide.

BMW R100
Anyway, back to the vehicle in question. “I always wanted to have a unique motorcycle,” says Karles, “the bike that I couldn’t find in any store. I have never done any job on a bike: I have never changed brake pads or removed the battery, so thinking about a custom project seemed to be an impossible mission.” Karles decided to give it a go, and found an R100 RT from 1982 that was the perfect base for his project. “I started to work hard with a lot of enthusiasm and patience, looking for accessories, removing all the parts I didn’t want, and trying to fix the new ones. At my side I had Jerry Churchill’s book, BMW 2-Valve Twins 1970-1993—a great tool for beginners like me—and also the help of some ‘masters’ from the BMW Classic forum.

BMW R100
“The main idea was to get a comfortable riding bike with a cool look, and trying not to spend a lot of money. So I went for the Scrambler style, with a high handlebar, solo seat and off-road tires. After three months, this is the result. Hope you like!”

BMW R100
BMW R100

  • elven

    A real motorcycle!
    Useful on road and for runs on decent hard trails.
    Looks simple and well proportioned too.
    What a relief ;-)
    Thanks Chris!

  • BoxerFanatic

    Love to see the BMWs. But then again, I am a boxer fanatic…

    This one looks very real-world, and effective.

    Well done, and fantastic first effort by the owner. Kudos.

  • Gebeme

    I love it! I still hate boxers but I love it.

  • Untitledmotorcycles

    Really good photos. If you like BMW boxers check out our latest builds and our first project on our blog and facebook. Thanks Adam

  • Greevous

    Great look, really well put together. Nice work!

  • Kevin

    Very sharp bike .. excellent work

  • This is a bike
    I can certainly like

  • Steve

    Why do they call flat twins boxers?

    • Den

      Not just twins, but all horizontally opposed flat cylinder layout engines, Douglas, Honda Gold wing, VW, Subaru, Ferrari, Alfa etc. I believe it is because as the pistons move in their cycle, which occurs symmetrically in this layout it resembles the action of two gloved fists punching each other, like the beginning of a boxing match. This is what I read somewhere once a long time ago. Correct me if I am wrong.

      • Den

        Oh and I love BMW twins. this one is not completely to my taste but he has put in a great effort and if it suits him that is just fantastic. I would love to see some work done customising the early oilheads too, they have been around for a while now and there is a lot of potential, even though they are very complex.

        • elven

          and decent oilheads are becoming cheaper than worn-out airheads too!

        • Oilheads have a lot of potential – good power of a modern engine and the simplicity (both mechanical and electronic) that lets you work on one without a dealership diagnostic computer. They also have a very distinctive look, different from the ubiquitous V-twins and transverse-fours, and also very classic.

          If you like BMW customs, BMW Motorcycle Magazine has at least one every issue. Looking forward to the next one coming out in about a week.

      • Steve

        Thanks Den, but surely the only engines that do that are opposed piston types, Leyland L10s, for instance? I think this is a fairly modern thing; nobody ever referred to a Douglas engine as a boxer. The only engines I can think of where the pistons moved like a boxer’s fists were those lovely little Rumi engines from the fifties, horizontal parallel twins with 180 degree cranks (I think). I remain puzzled. Can anybody else shed some light?

    • BoxerFanatic

      There is a difference between a 180-degree V-twin, and a true boxer twin. They look alike on the outside, but they differ at the crankshaft.

      A 180-degree V-2 has both connecting rods connected to the same crank journal, like most other V-twins, or V-engines of most cylinder counts. Since the cylinders are 180 degrees apart, the pistons are reverse of one another’s motion. As one piston rises toward TDC, the other falls toward BDC. The forces of the pistons both go the same direction at the same time.

      A true boxer engine has independent crank journals for each piston, and the journals are 180 degrees apart, just like the cylinders are. The pistons both rise away from each other at the same time, and fall toward each other at the same time. The forces of inertia cancel each other out for perfect balance.

      One of the other advantages of a boxer engine design, is low engine center of gravity. A BMW boxer’s CG is a couple inches lower than a V-engine of similar design, such as a Moto Guzzi, or a Honda CX. Honda did water-cool some of those designs, both boxer and longitudinal twin, and add cylinder count to their version of the boxer engine to four, and then six cylinders.

      As Den mentioned, it resembled a boxers fighting each other on the upstroke, so it was nick-named the “boxer” engine.

      Most of those that Den mentioned are boxer engines, except the ferrari. The Ferrari Colombo V12 was flattened to 180 degrees for the 365BB, 512BB, and 512 Testarossa, but it wasn’t a true boxer, it was a 180-degree V. However, a V12 at any angle has innate balance by a 60-degree firing order, and some pistons cancel others out, like a doubled inline 6, so a 180-degree V12 is pretty darn close to a true boxer 12, and there are plenty of crank journals in there already.

      Plus, unlike cars, BMW and Ural (russian duplication of older air-cooled BMW, where newer BMWs are air and oil cooled) motorcycles make the valvetrain and sparkplugs very easy to change. Most boxer cars are a pain in the neck to change spark plugs, or adjust valves if needed, because the heads are right up to the chassis rails. On a bike, they are out in the open, but vulnerable to hitting the ground. That is what crash bars and skid plates are for, I guess, if one can’t keep the rubber side down at all times… which happens to pretty much everybody at some point or another.

      • Steve

        A complete and technical explanation, for which I thank you. The only area to which you did less than complete justice is the name; why are flat twins called boxers? I write as a man who has owned 2cvs, Beetles, and still owns an R80, all flat engines, none of them described as boxers until BMW started it twenty odd years ago. Oh well.

        • BoxerFanatic

          I’ve only heard the analogy of the pistons’ motion (against each other, rather than *with* each other like a 180-degree V engine) resembling people boxing in a fight. Not even sure who first coined the term.

          Whether it is the pistons approaching each other simultaneously at BDC, or extending toward TDC on it’s connecting rod, like a fist at the end of a boxer’s arm, opposite of the opponent’s arm on the other side, I am not sure, but I can understand the analogy either way.

          But a 180-degree V, or any other V engine doesn’t do that the same way.

          I just tried to gain some more knowledge of the entymology, but that is about as deep as I find on a cursory search. I’d love to hear more about it myself.

      • Are there any 180° V-twins that are not boxers? I’m not aware of any.

        Don’t forget to mention the big safety advantage of a boxer motor… unlike a flat-sided bike, a lay-down doesn’t mean a pinned leg.

        If you ever get the urge to build a tiny R-bike replica that is fully functional:

        • BoxerFanatic

          As I mentioned… the Ferrari Colombo V12 got flattened to 180-degrees for the Berlinetta Boxer, and the Testarossa/512TR.

          It was a 180-degree V, not a boxer, as corresponding horizontal piston pairs shared a crank journal, just like the narrower-angle V12 versions of the engine. There may have been others. I am not sure about the horizontally opposed helicopter engine used in the Tucker, or other aeronautical flat engines, like Lycoming.

          I would think that engines designed from scratch as horizontally opposed, rather than adapted from narrower angle engines, would have specific-designed crankshaft to take advantage of the “boxer” inertia cancellation.

          • I said V- *TWINS*, not V-others. You mentioned the idea of 180-degree V-twins that are not boxers, and I’ve been trying to find any examples… my question was if you were aware of some.

          • BoxerFanatic

            Oh, I see.

            I don’t know of any flat twins that are 180-Vs… but then again, I don’t know of any companies that have had V-twins that have adapted them out to 180-degrees. BMW, Douglas, Ural, and those, have pretty much started from a clean sheet for a boxer twin, or copied a boxer twin.

            Plus the vibes of just one pair of cylinders going back and forth in unison would probably shake the engine to pieces, without being balanced with other cylinder pairs out of phase.

      • gebeme

        Thanks for your explanation. That was really interesting and well written. (Hope that doesn’t sound sarcastic because I am serious)

        • BoxerFanatic

          Thanks for the compliment. I hope it helped. I was sorry to see above that you said you hated boxers.

          Nothing can be everyone’s favorite, though, I guess. Nothing wrong with that.

  • iRivas

    I like this bike just as much as the one that was posted before. Hell, sometimes we talk crap about the bikes that Chris puts on this website, but I’m willing to bet $10 and a bottle of rum that we would take any one of these bikes if someone said, “here, it’s yours.” Enjoy the bikes and don’t make them so complicated, after all, it’s just a motorcycle and that’s what we love, an engine and two wheels.

  • Saginawdan

    Love it – The black with white trim sets it off perfectly – not a color combination one sees very often.

    For those not familiar with boxers – boxer engine cutaway schematic:

    • joe momma

      …according to that link the new boxers have lost the pushrods and maybe some of the valve cant??????……(and a swell trivia question)

      • BoxerFanatic

        That looks like a hex-head (hexagonal-ish head shape, with a spark-plug lead boot from the center to the aft edge of the valve cover. (air heads are like the bike pictured here, oil-heads are more rectangular. Hex heads are the newer 1200cc engines)

        But the newest BMW engines boxer twin engines, such as the HP2 Sport, R1200GS, LT, and R are DOHC, and visible by the spark plug lead boot coming up from the bottom of the valve cover, but otherwise the same hexagonal shape.

        The dual cams are a bit different than most, though, as the cams activate one intake and one exhaust valve per cam, not one cam for both intake, and the other for both exhaust. The cams are horizontal, but the intake valves are the aft upper and lower, the exhaust are the front upper and lower, as oriented on the bike.

  • mbrashier

    gorgeous. Great job!

  • Guest

    In the immortal words of sportscaster Senor Andrés Cantor,

  • I love it when a subliminal hint (from yesterday) works. Thanks, Chris!

  • Sandramiller5956

    I really like the Scrambler look on this old BMW. I wonder what it weighs? Every time I mention a Sportster Scrambler project the guys online tell me what a heavy Pig Im working with. I still think the Scrambler style is a great look on these non concours good running older bikes. Just about perfect for Sunday morning rides on less than perfect roads. Triumphs, BMWs and Sportsters all make fine Scramblers.

  • Markspoon

    Porsche Boxer, everything by Subaru too are boxer motors.

    The explatations of boxers sharing opposing blows sounds good to me too.

  • MaSK

    Dangerous post. I’m in the middle of restoring an R80GS but this look just might tempt me to the dark side of customising it instead.

    • elven

      Go for it, you know you really want to ! ;-)

      • Den

        I really like the idea of turning a GS into a roadster, do it!

  • yep this is a nice bike and I agree customising these old boxers makes a nice change – looking forwards to finishing my one later this year

    • elven

      I used a Taylor Made back wheel on my old V-max (in y2k), nice but heavy; any lighter with his more recent designs?

      • yeah really pleased with the wheels – they are only 3.5″ wide so weight is OK – and fortunately the girl in red dosent come with them!

  • Edbotsko

    Nice scrambler build…That front fender is more for dry, hard surfaces, but other than that, I’d ride it….

    • Den

      Does the woman in red lingerie improve the wheel balance?

  • Karlesvives

    Thank’s to all for your comments!!! i really appreciate all the opinions because it help me to improve and get a better result for the next custom project…Thank’s!
    If somebody wants to see how it was the bike i leave a link where you can see some pics

    • Wes

      thanks for the link!

  • BoxerFanatic

    I keep coming back to those front brakes… they look very large, especially the carriers. (not a bad thing)
    I wonder if they are aftermarket, or from which model of airhead BMW…

    • Karlesvives

      The front brakes are made handcrafted by a specialist in steel and an also an a special piece to fix the brake calliper

  • hot bike, great job

  • Badbike69

    I never liked BMW, but BE presented some custom BMWs, that I changed my mind. Thank you.

  • Pod3.5

    It looks like the brake lines are unsupported. They used to attach to the RT fairing but are now carrying the weight of the flexible brake lines on the short rigid lines……these WILL snap.

  • Wes

    stunning, and very real world indeed – if i am correct, the subframe is stock, and the rear mudguard looks like a trimmed down version of the stock one. Front mudguard and tank are stock, and I think the seat comes from one of the R100GS’s. Paintwork is stunning – a gorgeous motorcycle all round. I love the RT and ride one regularly which belongs to my father – I’ve been wanting to customise one for a long time now and this is right up the alley of what I was thinking of so it’s good inspiration.

    • Karlesvives

      Thank’s Wes for your comments!… as you say, the subframe, the tank and the front mudguard are stock. The seat is what the german police used on the rt for more comfortability and solo riding. The rear mudguard is from an old spanish enduro bike. About the “set of clips ons an rear sets”, i don’t understand what you mean..sorry my english is not so good!

      • Wes

        thanks for the info on the details – i am now better informed for my hopeful project one day! by clip ons and rear sets, i mean the low handlebars and footpegs mounted further back that you would find on a cafe racer – so what i’m saying is – this bike (the paint scheme and finishing touches) could even look good as a cafe racer!

  • Wes

    just 2 add another 2 cents – another thing about this bike, is that it would look just as good with a set of clip ons and rear-sets :D