In 1973 BMW celebrated the 50th anniversary of its boxer twin with its most audacious road bike ever — the R90S. Sporty at heart and with the Z1 in its sights this crazy kraut took on the Japanese and won.
It’s strange how history is sometimes tainted with hyperbole.
The arrival of the Honda CB750 in 1969 turned motorcycling on its head. Or did it?
On its launch it in fact had an inferior power-to-weight ratio, and was only slightly faster than the Norton Commando released a year earlier.
Even Kawasaki’s equally seminal Z1 offered more in terms of flash and dash than it did in real performance terms. Check through the Isle of Man TT database and search for Production TTs won by the 11 — you’ll not find one: for while the 11 was a powerhouse with 82bhp, it was also the full 16 ounce New York Steak, weighing in at a hefty 246kg. The Z1 certainly had swagger, but when it came to holding a line and a racing line in particular — well, that was a whole different thing, hence the ‘Flexi-flyer’ moniker adopted by proddie racers in America and Australia.
All of which seems to be an odd introduction to the BMW R90S. But it goes some way to explaining how BMW’s pushrod two-valve horizontally-opposed flat twin could not only hang in there with the new Japanese, but beat them: on the road and on the track. The R90S won the inaugural AMA Superbike title in 1976 and only lost out on gaining that title again in 1978 after a penalty awarded against a contentious start line ‘error’. The R90S also placed well in production-based racing elsewhere, winning the 1978 Canadian Superbike title, winning the gruelling 10 lap lOOOcc Production TT in 1976 and scoring podiums in the Coupe d’Endurance.
Point being, the brains in Berlin had created a potent machine. Some 67bhp wasn’t much to brag about, but in a package that weighed 215kg it was substantially lighter than the Japanese fours — exceeding the Honda’s power-to-weight ratio and getting close to that of the Zl. Just as importantly BMW had assembled a chassis — suspiciously like a Norton Featherbed, we think — that was more accurate, more stable — and just plain better handling than the fours. The BMW lacked the new-age allure and soundtrack of the fours, but it proved an even match, and more, when it came to speed and lap times.
The R90S’s story started in 1969, the year BMW launched its new generation ‘Type 247’ motor, seen initially in 500cc (R50/5), 600cc (R60/5) and 750cc (R75/5) capacities. While not exactly hot rods — the R75 made 50bhp — the massively redesigned motor and chassis (using car type technologies employed by ex-Porsche engineers) had plenty of potential for development. This potential was realised in the R90S in late 1973 -the new bike effectively being a big-bore R75 (the bore increased from 82 to 90mm) sporting a strengthened bottom end, new gearshift, new alternator and Dell’Orto 38mm ‘pumper’ carburettors feeding a high compression (9.5:1) head. There were tweaks to the chassis as well, not least an added 30mm of travel on the forks to deal with the braking forces generated by the new twin-disc front brake set-up.
Hans Muth — who would go on to design BMW’s streamlined R100RS and Suzuki’s Katana — created the RSOS’s handsome profile, including the very effective nose fairing finished off — quite shockingly for BMW — with 70s-flash smoked paint effects in grey and later in orange. Tall and lean, the R90S had the look, the essence, of brain over brawn, but that wasn’t strictly true. The extra 17bhp had come easy, and so did even more, as tuners discovered both in Europe and America. The AMA Superbike winning But!er& Smith R90S’s allegedly pushed out a huge 102bhp while weighing a handy 175kg.
Ali this added an exciting new dimension to BMW, which hitherto — despite a fair racing pedigree — had sold units off a reputation for making excellent gentleman’s tourers. The R90S didn’t break the mould as such, but it certainly added the prefix ‘fast’ to the tourer bit. And it’s important to remember what the bike gave to the buying public.
Top speed was 125mph on a very good day, but significantly it was the BMW’s high touring speed that really set it apart. Kawasaki’s Z1 might have been capable of 132mph, but it couldn’t cruise at the BMW’s ll0mph for hour after hour, in fact the 1976 Production TT win by Helmut
Dahne and Hans Otto-Butenuth reflects that strength. Over 10 laps the R90S decimated the field achieving a race speed of 98.92mph. As a percentage of the bike’s top speed that’s phenomenal — John McGuinness on his Fireblade would have to lap at 150mph to match that ratio — and it’s also amazing because you have to take into account the time lost in pit stops and the condition of the course back then (massively bumpier and in places tighter than today). Another BMW placed second and the first Japanese bike was a Honda CB750, languishing back in seventh.
It was this real world strength that owners loved, and it befuddled nonbelievers. Top sports photographer Don Morley used an R90S as his transport to and from GPs back then, aided in the mission, of course, by those impressive BMW-Krauser panniers that were uniquely designed to fit so neatly with the bikes.
“The R90S was fantastic for the job not least because max speed was cruising speed, the saddle was super comfortable over long distance and I could carry all my photo gear in the Krausers,” remembers Don. «Most importantly though the headlight was far better than anything else about on two wheels in those days, so unlike all the others I could keep up the same high speeds at night.
“We would leave somewhere like Hockenheim during daylight, along with Sots of other UK fans riding big Hondas and Kawasakis etc, and like me a!! going like hell for the midnight ferry — which in those days was the last, i would watch them disappear into the distance but it was a tortoise and hare job as I would always repass them after it got dark and they got slower and slower due to the Jap bikes all having lousy lights. More than once I watched these so called quick guys turn up just as we sailed.’
The R90S certainiy re-established BMW in the sports touring market, if not exactly the sports market (despite the racing successes). BMW built it for three years before taking the next logical step, with the streamlined full-fairing R100RS in 1977. Time, though, was not on the old air-cooled boxer’s side and the R90S was certainly the sporting pinnacle for BMW in the 1970s, Their next direct broadside on the Japanese would not come until 1983 with the K100 four.
The R90S is a stunning machine, but given the era (early 1970s) we’re trying to remember ages-old procedures. There’s an ignition key that is concealed within the fairing on the left headlamp bracket. Two fuel taps. And a choke lever, under the seat, on the left and rear of the engine. There is a small array of idiot lights though. The top one quaintly reads ‘brake failure’ -quite how a failure is detected ! don’t know. Less perplexing, and so more welcome, are a clock and voltmeter nestling in the fairing — good touring-biased dials. The R90S looks tali and lean, but on closer acquaintance it’s not that tall and in fact the bike feels smaller than you anticipate, everything is that little bit more close-coupled than you expect (it’s 30mm shorter than a Zl). Even the bars are that little bit narrower, barely projecting beyond the fairing — which itself is smaller and lower than it first appears.
It fires into life with something of a left-right lurch as the pistons lugubriously throw themselves out and in, causing the starter motor some strain. When the spark catches, it all smoothes out, there’s no mechanical thrashing, it’s all sounds suitably well engineered, the only quirk being the quiet ‘popping’ from the phenolic disc and spring’ engine breather.
The riding position is positively old school. The seat feels flat, like a plank (only well padded), the footpegs are directly beneath you, not rear-set, the narrow bars mean you present but a modest obstruction to the wind blast. It’s all very neat. Select first, let out the clutch -feeling the rear end rise in reaction to the shaft drive — and you’re away pretty sharpish. Immediately the whole plot feels taught. The engine responds obediently to the throttle, the frame keeps the plot tracking laser-beam sharp, even the brakes offer decent performance despite misgivings you might hear elsewhere.
The longish travel suspension deals with bumps and potholes with casual efficiency and when the curves come up it tracks a line with clipped accuracy. There’s a steering damper sitting over the top yoke but when riding at highway legal speeds it’s not needed.
The R90S is scribing (2H) pencil and compass clean curves on a crisp white page, whereas the Z1 — as I recall from a recent test — would want to dash off something of a freehand slash, complete with smudges as your hand weaves and wobbles over the page.
The power isn’t half bad. You can understand how back in the day the Z1 would have been so exciting — the howl of the four sounds so good — but its actual acceleration wasn’t that much quicker. Riding the R90S, again there’s so much efficiency you sense there’s no wastage, it’s putting all its power down.
It shifts gear neatly and despite initial concerns over dodgy behaviour from the shaft drive when down-shifting the R90S remains spot-on.
And still, nearly 40 years after its build, this R90S seems to think nothing of high speeds. On the run to the photoshoot it was happily cruising at a healthy 85mphr and even with a five-speed box it wasn’t rewing overly. And you could tell that 85mph was the bottom end of its fast-cruise range.
Very quickly you get the picture — this bike is very fast, very good handling — and very comfortable: a real pleasure to ride.
BUYING AND OWNING
These early Type 247 BMWs certainly aren’t getting any cheaper. Prices are on a steady rise, with the R90S at the spearhead. So when it comes to buying -you might want to sit down — be warned the R90S is almost as expensive now (comparatively) as it was back in the day.
Back then it was a whole lot more than say a CB750 (BMW has never been shy with applying premium price tags) and a good R90S today is going to set you back anything between £6500 and £7500. If we take sandcast CBs out of the equation, that’s about the same relativity and a fair 50% more than a decent CB750. Of course if you want to get really happy with the cheque book there’s currently a Gus Kuhn R90S-based endurance racer up for sale via a German dealer for a steady-away €21,000 (£18,000).
The racer example aside, that’s still a considerable premium over any other BMW ‘airhead’ — you can find the lower-spec R90/6 sibling for around £3500 — but then the R90S was the real McCoy, the history maker, and with limited numbers — officially there were 17,455 manufactured between 1974 and ’76 — and with global distribution and natural wastage you’ve only a limited number in the UK to buy from.
Do, though, check to ensure you are buying a real R90S and not a copy, based on an R90/6 or maybe an R75/6. There wasn’t that much between the models and like Laverda Jota copies they’re fairly straightforward to create. It’s an easy check online for a definitive list of frame numbers for the R90S.
There’s almost no point in suggesting ‘tatty’ values as you’ll struggle to find one. Specialist dealer James Sherlock recently broke an R90S via eBay and the bike was stripped clean quicker than a committee of vultures cleans up a downed wildebeest.
There are very few parts on the R90S that are specific to this model alone, so spares are readily available at reasonable prices. There is a list of ‘acceptable’ modifications as well — unless you’re after a concours winner. Look out for twin spark head conversions, for electronic ignitions (Boyer Bransden is very popular). Also, chassis-wise, where originally the front disc brake featured a cable actuation from the handlebar to a hydraulic master cylinder under the tank, it’s common to find a full hydraulic system fitted with conventional handlebar-mounted master cylinder (for better performance and feel). Stainless steel is much favoured, for complete exhaust systems and for wheel spokes, while aftermarket shocks from the likes of Hagon or Ikon are popular.
There were updates year to year, notably early R90Ss featured archaic /5 type switchgear. Likewise the brakes changed, starting with plain discs, later replaced by drilled ones. The spec on the motor and gearbox also improved significantly year to year — even mid year (BMW operating something of a rolling programme on updates). So later models are generally stronger. Colours changed too. TT silver smoke in 1974, then adding Daytona orange in 1975.
Very little goes wrong. The 1974 model suffered flywheel bolt failures but most should be sorted by now. And whereas previously we’ve mentioned issues with the Paralever shaft drive on later (particularly GS) BMWs, the shaft drive on the twin shockers is a solid bit of engineering that’ll see 100,000 miles and reputedly go another 100,000. BMW gearboxes can alsc wear out, there are many who suggest rebuilds will be needed anywhere between 50-75,000 miles. Otherwise look for good service history — your standard issue BMW owner will be fastidious with the paperwork.
BMWs do seem to illicit a Marmite reaction and that seems to hold for their classics as much as the moderns. The hairy-arsed among us that will love old Jap-fours, understand Laverdas and tolerate Ducatis, even accept Guzzis, still find BMWs just a sociological step too far. That said just as the S1000RR is making modern bikers reevaluate the brand today, so the R90S did back in the mid-1970s. Honestly, it took Pops Yoshimura years, tuning Zls up to 140bhp, bracing the chassis to hell and back, to get the better of the R90S.
And so today the R90S is a very practical, very usable classic: that’s expensive to buy, not run — you can ride an R90S almost as hard now as they were ridden then, without causing mechanical meltdown. German yes, but an awesome machine all the same.