Alan Cathcart was one of only two people to ride the BMW R1 Desmo, giving us a taste of what could've been the first Boxer powered WorldSBK machine... Photos: BMW/Arnold Debus
Thirty years ago in 1992, BMW unveiled its born-again Boxer R 1100, the descendants of which are still with us today in R 1250 guise. With the boxer’s return, BMW Motorrad management decided to develop a prototype Boxer Superbike racer, the BMW R1 Desmo
The road going Boxer R 1100 was a fuel-injected eight-valve twin with Telelever front suspension which underpinned the German manufacturer’s resurgence in the following decade, when BMW Motorrad’s sales volume tripled from a mere 30,000 bikes a year at the start of the 1990s to close on 90,000 units annually by the turn of the millennium. BMW sold 194,261 motorcycles to customers in 2021 – and that spiralling growth began exactly 30 years ago this year.
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But back then, at the same time as creating an all-new high-cam five-speed engine, code-numbered R259, to power a resurgent Boxer family, BMW Motorrad’s Technical Director Dr. Burkhard Göschel gave his 200-strong team of R&D engineers another task. This was to develop a liquid-cooled DOHC six-speed Superbike racer, still employing BMW’s trademark flat-twin Boxer engine format, but developed to deliver competitive performance versus the 90º V-twin desmo Ducati that was by then established as the bike to beat in World Superbike racing.
For the Italian company won the title in 1990 when Raymond Roche overturned two years of Honda domination to prove twins could indeed beat fours – especially with a 250cc capacity advantage (1000cc vs 750cc) and much reduced 140kg minimum weight limit, against 165kg for fours and triples.
However, BMW hadn’t road raced competitively for 15 years, not since the dawn of Superbike racing in the mid-’70s when the Butler & Smith R90S Boxers ridden by Reg Pridmore and Steve McLaughlin won both the first-ever Daytona Superbike race and the inaugural AMA Superbike title, while across the Atlantic Helmut Dähne took his R90S BMW to victory in the Isle of Man Production TT and in Australia Tony Hatton was very successful on the Boxer twin.
Since then, the German company had sat on the sidelines while its Italian counterpart Ducati swam against the tide with its desmo V-twin, eventually turning it into the dominant force of Superbike racing. At the same time, though, BMW Motorrad’s four-wheeled cousins had transformed their brand image from slightly stuffy to ultra-sporty via a racing campaign yielding serial Touring Car race wins and titles, with spinoff showroom success in their wake.
So, as a means of following in the tyre tracks of their car counterparts, and endowing the German firm’s motorcycles with the same kind of sporting allure as the products of its car division, BMW Motorrad management decided to develop a prototype Boxer Superbike racer, to see if it could be made competitive with the Ducati paragon – in which case a customer street version would surely have followed, to allow the company and its customers to go Superbike racing with the result.
So in 1990, at the same time as producing the born-again Boxer road bike’s air/oil-cooled engine – commonly known as the Oilhead motor – BMW’s chief engine designer Heinz Hage and his R&D team set to work creating a second, completely different water-cooled flat-twin engine under the R1 label. But with a 1000cc ceiling for Superbike twins, this had nothing in common with the concurrent R 1100 volume production motor – indeed, BMW literally turned that design upside down to create what it was hoped would be a competitive and practical race package.
This entailed firstly reversing the layout of the traditional Boxer engine, by placing ancillary parts like the alternator and starter motor normally positioned on top of the flat-twin motor, instead beneath the raised cylinders of the R1, to help achieve the substantially improved ground clearance at full lean needed with slick tyres.
While retaining BMW’s traditional shaft final drive via the by then established Paralever rear end, an all-new six-speed gearbox was located beneath the motor rather than behind it as on street Boxers, driving through a sintered-bronze single-plate dry clutch with diaphragm operation. This transmission was readily extractable so that internal ratios could be swapped inside 30 minutes in the pit garage.
At the same time, Hage and his team rotated the horizontal Boxer cylinders 90° to deliver enhanced induction and a more rational riding position. So, instead of the exhausts exiting out the front of the sticking-out cylinders, and the throttle-bodies mounted behind them (where they usually interfered with the rider’s feet, often requiring the seat to be located further rearwards than was ideal in terms of overall weight distribution), thanks to the extra space provided by the RennBoxer’s revised architecture, and the fact the engine was mounted high in the frame with the crankshaft no less than 520mm above the ground, on the R1 the exhaust ports pointed at the ground, and the intake at the sky.
This layout delivered 100 per cent downdraught for the twin 54mm throttle-bodies, each fitted with a single side-mounted injector, and a TPS throttle position sensor linked to the Bosch EFI. These were fed via vertical ducts from the airbox located in the front part of the fuel tank shroud, with the 18-litre fuel load carried behind in a tank extending downwards. At the same time, the four-valve cylinder heads with chain-driven double overhead camshafts saw the lower (exhaust) camshafts staggered slightly so that they snuggled closer to the piston than the inlet cams, in order to further improve ground clearance at full lean.
This trick was later emulated by Ducati on their 1996 V-twin’s lower, horizontal, cylinder, to let the engine be mounted further forward in the frame, without the front tyre hitting it under braking. But BMW had the idea first, same as the R1’s 98 x 66mm engine dimensions, later adopted by Ducati themselves in 1995, and by Suzuki on its TL1000R 90º V-twin Superbike later in the decade.
But dues were reversed when it came to the R1 Boxer’s cylinder-head design. For Burkhard Göschel had been a top engineer at Daimler-Benz before joining BMW’s car division in the 1980s, transferring to the Motorrad side in 1989 by which time the R 1100 Boxer project was well under way, its overall format having been agreed back in 1986.
“Göschel was a fan of desmodromic positive valve operation… from studying the ultra-successful Mercedes-Benz W196 GP racer during his time there.”
Göschel was a fan of desmodromic positive valve operation, not only because of its proven worth in Ducati’s Superbike application, but also from studying the ultra-successful Mercedes-Benz W196 GP racer during his time there. This dominated the Formula 1 World Championship for two seasons in 1954-55 with its desmodromic straight-eight engine, which also powered Stirling Moss and World Sidecar champion Denis Jenkinson to victory in the 1955 Mille Miglia – the only time a non-Italian car ever won that gruelling race.
Göschel reasoned that the radical camshaft design with wild valve timing and extreme lift which a desmo cylinder-head’s positive valve operation permits, was one reason for Ducati’s twin-cylinder Superbike success, not to mention the extra power obtained at higher piston speeds without resorting to the pneumatic valve gear then already commonplace on Formula 1 cars, but impractical for use on a streetbike that could provide the basis for Superbike homologation.
So BMW’s cylinder-head expert Georg Emmersberger was directed to develop a four-valve desmo cylinder-head design for the R1, with its pairs of titanium valves (38mm inlets and 33mm exhausts) set at a very flat included angle of barely 20 degrees. Thus the plain-bearing one-piece crankshaft which supported a pair of Pankl titanium conrods (another feature shared with Ducati) mounted side by side on it, each carrying a forged two-ring Mahle piston running in a Nikasil-plated cylinder, drove a half-time idler shaft mounted beneath it.
This in turn drove twin chains running to the two (lower) exhaust camshafts, whence a secondary chain in each head drove the inlet cam. This modular layout was a chain-drive copy of the bevel-drive valvegear in BMW’s legendary Rennsport 500cc Boxer GP motor, which finished runner-up to the four-cylinder MV Agusta in the 500GP World Championship in 1956, as well as winning no less than 19 World Sidecar GP titles over a 21-year period.
But each cylinder-head’s valvegear thereafter followed the Ducati model, with four lobes on each camshaft operating four rockers, two per valve – a conventional finger-type one to open it, and a forked one to close it, with small low-pressure springs as on the Italian bike to seal the valves properly at low revs, and provide for easier starting.
To house the engine, BMW commissioned a dedicated twin-spar aluminium race chassis from their established supplier Nico Bakker, the Dutch frame guru who already in 1990 had created a prototype ProTwins racer for BMW tester Herbert Enzinger to race under the aegis of BMW dealers Handrich & Mayer. I myself raced many times against this factory prototype powered by an air-cooled R100R two-valve Boxer motor, which employed a Telelever front-end as part of the R1100 R&D programme, and was impressed enough with the way it handled to sign up a few years later to race the Saxon Triumph, whose unpatented Saxtrak front-end was in fact copied by BMW in creating the Telelever. In the winter of 1991/92 Bakker produced an evolution of this chassis to create the R1, but with the bulkier DOHC desmo engine mounted much higher in the frame, for extra ground clearance at full lean on slick tyres.
Fitted with Brembo brakes, Marvic 17-inch wheels and a fully-adjustable WP shock at each end, the result was unexpectedly compact, and reasonably light for a shaft-drive twin, according to Bakker. “We built three frames, and I was pleased with the way they came out,” recalls Nico today, “although we had to make a new housing for the drive shaft so as to shorten the swingarm compared to the R 1100 streetbike – we got it down to just 1465mm, which is short for a BMW. Plus, despite the heavy cardan unit we ended up with a 50/50 weight bias, which came from mounting the engine quite far forward in the wheelbase, since there’s no deflection from the Telelever front-end.
The weight itself wasn’t bad, either, after our expert panel-beater Cees Smit made the original fairing, seat and the fuel tank in aluminium, and BMW took carbon moulds off these. Once fitted with carbon fibre bodywork, which was quite rare back then, it weighed in at 160kg dry, so it was competitive with the fours, though quite a bit heavier than the Ducati’s were allowed to be at that time.
To underline this, Doug Polen’s factory 888 desmo V-twin with which the Texan won the second of his two World Superbike titles in 1992, weighed in at 142kg with oil and water when I tested it at Misano midway through that season – a ride that was apparently concurrent with one of Herbert Enzinger’s tests of the BMW R1 further up the Adriatic at the Rijeka circuit. “We finished the bike in the Spring of 1992, and wanted to go somewhere that was quiet and out of the way to test it,” recalls Gert Helm, Enzinger’s race engineer who built up the R1, and looked after it during his rider’s test programme.
“We went there a couple of times, and were making progress – but there were two problems we couldn’t overcome. One was aerodynamics, because with a Boxer engine the bike couldn’t help being wider than a Ducati – and the second was power. We began with 132bhp on the first dyno run, and eventually got 140bhp at the crankshaft from the engine, at 11,000rpm – but we felt we needed another 15-20bhp more to be truly competitive, and we couldn’t see how to obtain this while still having a usable power delivery. For BMW, it’s not enough to score points finishing in 8th place – we have to win races. So at the end of the year, our management cancelled the programme, and the only complete bike we ever built went into the cellar in Munich. Pity!”
There it might have stayed, but for BMW’s praiseworthy Mobile Tradition programme, which sees some of its most historic products and rare prototypes exercised in public. Add in the persuasive charm of the Duke of Richmond, whose annual Goodwood Festival of Speed held at his magnificent English country home and attracting 180,000 spectators each year is one of the world’s major showcases for such vehicles – and it was inevitable the R1 Desmo should finally make its public debut there in 1999, returning two years later for a repeat airing in the hands of Herbert Enzinger.
“I was given the exclusive chance to give it a final run… only the second person after BMW tester Enzinger to sample the R1 desmo Boxer”
But with the decision taken to mothball it for good in the BMW Museum, I was given the exclusive chance to give it a final run round an improvised circuit at a Luftwaffe base to the west of Munich as only the second person after BMW tester Enzinger to sample the R1 desmo Boxer in its Superbike guise. In doing so, I hoped to be able to answer the questions so many BMW fans will be wondering: was the R1 really any good, and if so, why didn’t it reach production?
Lined up alongside a then current R 1200 S model, and the 1976 ex-Steve McLaughlin R90S Daytona-winning Superbike which BMW had brought along for me to ride as well, the R1 Desmo looked sharp and not particularly big – actually, it seemed the shortest and most compact of the three Boxer bikes.
However, viewed from behind the bike is indeed pretty massive-looking, thanks to the broad span of the Boxer motor positioned so high up in the frame that it dominates your view in a way the lower-slung hi-cam or pushrod Boxer motors never do – an impression of width emphasised by the fat cylinder-heads reaching out the sides, each with four rockers and two camshafts.
Clamber aboard, and you’re faced with a very distinctive riding position, with what seems a long reach over the shapely fuel tank-cum-airbox shroud, out to the flat-set handlebars. But that’s because you have to wrap your arms around the vertical intake ducts leading down to each cylinder-head’s throttle-body, making the BMW seem immediately as wide as it really is.
Because there’s no getting away from it – those cylinders do stick out a long way, and although there’s no carbs to interfere with your feet, as on the 500cc BMW Rennsport classic racer I used to ride in Historic GPs, you’re always aware of the mass of metal parked crossways in the frame beneath you. Getting your feet aboard means tucking them inboard of the wings of the fairing section carrying the BMW badge, with the result that you feel pretty much wedged in place, making it awkward to move about the bike so as to hang off it in turns.
Even without the variation in surfaces right in the middle of the most testing corner on the Luftwaffe test track, the R1 desmo didn’t feel very agile, though it’s evident from looking at the bike without bodywork that the mass is centralised in a way that modern MotoGP designers would die for to optimise their bike’s handling. The BMW’s Telelever front-end with the compliant WP shock is quite supplely damped, but offers almost no dive under hard braking, resulting in constant, predictable steering geometry.
Also reminiscent of the MotoGP paddock was the remote starter Gert Helm used to fire up the RennBoxer motor, before it settled to a 1,500rpm idle speed. But once aboard, even as the revs mounted towards the 8,000rpm rev limit I’d been asked to observe, there was no hint of any undue vibration thanks to the Boxer twin’s inherently perfect primary and secondary balance. The flat-twin engine felt potent and perky, but completely smooth, although running it up to 10,500rpm just the once on the white-faced tacho showed that vibration did intensify considerably as revs mounted towards the peak power mark.
“This was the real reason they cancelled the project,” insists Nico Bakker. “At the high revs they needed to get competitive power, the vibration got so bad you couldn’t ride the bike for long. We were worried about the frame cracking, although it never did – but you couldn’t race it like that.”
However, even at the reduced revs I’d been asked to observe the R1’s power delivery was pretty vivid while totally linear, with a strong pickup from a closed throttle that at first had the treaded rear Metzeler Racetech tyre fitted new for the test scrabbling for grip, until I got it warmed up. The throttle response wasn’t quite as brutally snatchy as the R7 Yamaha would be six years after the BMW’s birth, but it was still pretty jerky and I’d have wanted to make sure I had a less aggressive engine map in the ECU for a wet race – or to switch to as the tyres wore, in a dry one.
“We were worried about the frame cracking, although it never did – but you couldn’t race it like that.” said Nico Bakker about the vibrations…
There’s good drive from 3,000rpm up, making this a potentially usable road bike had it ever reached the street, but the true power threshold is 5,500rpm, when things pick up more strongly and there’s plenty of torque available for third-gear power wheelies when you hit a higher gear at the eight grand mark on the street-pattern gearbox, rather than rev it right out as Enzinger would have done.
I’m fortunate to have ridden dozens of Nico Bakker-framed bikes down the years, and they all have the same balanced feel and sane riding position that the R1 Desmo has, once you get used to having to drape your arms round those airducts. This means there isn’t undue weight on your arms or shoulders, and that the quite conservative steering geometry delivers predictable if slightly heavy steering. That’s an impression magnified by the sheer bulk of the R1 Desmo engine, which makes the bike seem wide and awkward at slower speeds in tighter bends, where it turned in quite easily thanks to the Bakker magic, but was then very heavy to lift up again for the exit, or to flip from side to side for a fast chicane.
The Telelever front-end felt really planted, though – after 10 minutes or so aboard the R1 Boxer it was yesterday once more, as I remembered all the advantages this Saxtrak design offers in a racing setup, especially braking hard on the angle over a bumpy surface, where the suspension keeps right on working to maximum effect even as you lean on the lever with your right hand. Despite the slightly soft response by modern radial standards of the period Brembo brakes fitted to the R1, I repeatedly noted this over the Luftwaffe track’s surface transitions. The BMW came out of this well, especially if I used engine braking to aid the slightly soft brake package.
Doing so didn’t get the rear wheel chattering, but it was the only time I really noticed the shaft drive and/or lengthways crank in terms of handling, as it rocked a little to one side as I blipped the throttle to backshift through the gears in the absence of a slipper clutch. Presumably the R1 motor must have an aluminium or even titanium flywheel, because there’s so little torque reaction from the Boxer engine this seems the only likely explanation. It’s sorted, whatever the reason.
However, you can’t get away from the size of the bike, even if the wide bodywork does deliver pretty good rider protection at high speed in sixth gear, which even at my 8,000rpm ceiling would have to be over 250km/h – the R1 was trapped at over 280km/h in testing, according to Gert Helm. The BMW über-Boxer felt solid as a rock at those speeds – which were also the only time the temperature needle didn’t scoot with a mission towards the 100ºC mark, and threaten to boil.
The water-cooled RennBoxer has a pair of radiators with a surprisingly small surface area parked in the flanks of the fairing, and even on a cool day they weren’t up to the job, regularly hitting that ton-up mark in slower sections, and running at just over 90ºC even in a straight line. Presumably a street version would have had a pair of electric fans to help cool it down.
Ironically, the R1 may have been a victim of the changing World Superbike rules, because if BMW had waited just a couple of years, they’d have seen Ducati’s decidedly unfair weight advantage first reduced, then eliminated. With the common 165kg minimum weight limit for all types of Superbike that was eventually introduced from 1996 onwards, irrespective of the number of cylinders, the flat-twin Desmo’s several extra kilos over its Latin V-twin counterpart, amounting to a 13 per cent handicap, would have been cancelled out.
That’s where the disadvantage truly lay that BMW management apparently felt their prototype RennBoxer suffered from – for at the point that Polen’s 1992 title-winning Ducati produced 134bhp at the gearbox at 11,200rpm according to the factory dyno charts I was shown when I rode the bike, the 140 crank-horsepower BMW wasn’t so far off the pace in relatively undeveloped guise.
I think what told most against the R1 was its frankly idiosyncratic architecture, which thanks to the bulky high-up engine and awkward riding position is definitely more extreme and hard to adjust to than, say, a modern SportBoxer like the R 1200 S. That and the overheating, which could surely have been fixed, were the only downsides of one of the great Mystery Bikes of the 20th century.
Could it have been a race-winner? Back in 1993, just maybe – but only on a fast, flowing circuit, and with a brave rider dedicated to exploiting its performance in the unique way its architecture demanded, for by mid-’90s SBK standards the prototype BMW R1 had a competitive power-to-weight ratio.
Could it, should it have been built for sale to the public? Yes, it should – it would have made a totally unique and completely individual Boxer sportbike, had BMW invested further R&D to refine it further, and round off the edges. But, don’t you just wonder how Ducati would have reacted at having a rival desmo twin in the marketplace – and a German one, at that!
1992 BMW R1 Desmo Prototype Specifications
ENGINE: Water-cooled DOHC eight-valve 180° flat-twin four-stroke with desmodromic valve operation and modular chain camshaft drive, 996cc, 98mm x 66mm bore & stroke, 12:1 compression ratio Bosch electronic fuel injection and engine management system, with two 54mm throttle bodies and single injector per cylinder, Dry sintered bronze single-plate diaphragm clutch, 6-speed gearbox with shaft final drive
CHASSIS: Aluminium twin-spar frame, front suspension: BMW Telelever with fully-adjustable WP shock with 110mm of wheel travel, rear suspension: BMW Paralever cast aluminium shaft final drive housing with fully-adjustable WP shock with 120mm of wheel travel, front brakes: 2 x 320mm Brembo steel discs with four-piston Brembo calipers, rear brake: 1 x 280 mm Brembo steel disc with two-piston Brembo caliper, front wheels/tyres: 120/70-17 Metzeler Racetec on 3.50 in. cast magnesium Marvic wheel, rear wheels/tyres: 180/55-17 Metzeler Racetec on 5.50 in. cast magnesium Marvic wheel, 24 degree head angle, 88mm trail.
PERFORMANCE: 140bhp@11,000rpm (at crankshaft), top speed over 280km/h, 50/50 weight distribution, 160 kg with oil and water, no fuel.
Owner: BMW Motorrad, Munich, Germany
1992 BMW R1 Desmo Prototype Gallery
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