BMW K100RS
‘I recalled the trip back from that Isle of Man test when, as we riders disembarked from the Steam Packet ferry, late on a cold night with many hours of motorway riding ahead, all of us had wanted to be riding the suddenly desirable BMW’
Roland swings a leg over one of the earlier in-line four Beemers
IT WAS WHEN THE BMW HIT TOP GEAR THAT THE memories came flooding back. Until that moment, admiring the gleaming condition of this unrestored K100RS had done little to make me recall riding one decades ago; nor had trickling through traffic at the start of my test ride. But when I got on to a main road, accelerated through the box into fifth and settled into a steady 140-km/h cruise, I was suddenly transported back to 1984.
Back then I'd been involved in a five-bike shootout on the Isle of Man, pitting the new K100RS against Japanese competition in the shape of Honda's VF1000F, Yamaha's FJ1100, and Kawasaki's GPZ900R. The softly tuned, softly suspended BMW had been outclassed by its harder and faster Japanese opposition on the demanding Mountain Circuit.
But as this immaculate navy-and-white BMW wafted effortlessly along the dual-carriageway, I remembered how capable and comfortable that original RS had been at a less frantic pace. In particular, I recalled the trip back from that Isle of Man test when, as we riders disembarked from the Steam Packet ferry, late on a cold night with many hours of motorway riding ahead, all of us had wanted to be riding the suddenly desirable BMW.
In truth, the K100RS never was a sports bike and should probably not have been included in a performance-based test against such opposition. The German four was arguably not even aggressive enough to have been labelled a sports-tourer, having been allocated that role largely because it sat in the middle of BMW's new three-bike family of four-cylinder models, which also comprised the naked K100 and the bigger K100RT tourer.
That trio of K-series machines, with their longitudinally arranged four-pot motors, certainly caused a stir back in 1984. The surprise wasn't just the arrival of bikes whose engine layout was new not just to BMW but to all motorcycling. What seemed almost incredible to many people back then was the firm's apparent plan to halt production of the trademark air-cooled boxer twins that dated back more than 60 years to the original R32 model. (In the end, the unexpected success of the dual-purpose R80G/S ensured the boxers' survival.)
BMW's bosses had decided they needed the additional power and sophistication of liquid-cooled four- and three-cylinder bikes to compete with the Japanese and the trio of K100s was the initial result. Although the three models looked completely different, with bodywork ranging from the standard bike's headlamp nacelle to the gigantic fairing of the RT, they shared a vast majority of the components. That included the 987-cc engine, which sat longitudinally with its cylinders horizontal and the crankshaft and drive shaft assembly on the right side.
On the left was the angular cylinder-head, featuring twin overhead cams and eight valves, which earned the K100 the nickname “flying brick”. Engine dimensions were very long-stroke, at 67 x 70 mm, designed more for low-rev torque than top-end power. The claimed peak output of 90 hp at 8,000 rpm was well up on that of BMW's boxers, but substantially down on Japanese figures even before that 1984 season, which saw the stakes raised by the GPZ900R and
FJ1100, both of which were over 20 hp more powerful.
The K100 trio also shared their chassis layout, based on a tubular steel frame that used the engine as a stressed member. Suspension comprised conventional telescopic forks, plus a Monolever singleshock rear end with the swing-arm pivoting on the engine. Apart from varied spring and damping rates to suit their differing weights, the three models' units were identical. While much of the superbike world was heading towards 16-inch front wheels, the BMWs relied on a traditional 18-incher, with a 17-inch rear.
Of the three K-models, it was the RS that was the most eagerly awaited. Its half-fairing promised a worthwhile advantage over the naked standard K100, helping to justify the marque's high prices. And the RS was enough of a long-distance machine to satisfy most of BMW's traditional customers, ahead of the more specifically touring oriented K100RT, which arrived shortly afterwards.
The RS was also the most stylish of the three, which is easy to understand when examining this example, a limited-edition model from 1989 whose paintwork in BMW's navy-and-white Motosport colours was enough to earn the label K100RSS. It was in nearimmaculate condition and standard apart from its ABS system having been disabled ― a common tactic with K-bike owners because BMW's early anti-lock systems often give problems.
The only other fault I noticed was with the dashboard's clock, some of whose digits were missing. Evidence of sensible design included the fairing and screen, which was usefully lipped to throw air over the rider's head, and the fairly narrow bars which gave a slightly leant-forward riding position that offered plenty of room in conjunction with fairly low foot-rests.
Less sensible, in my and most other riders' opinion at the time, was BMW's complicated new switchgear, involving thumb-operated indicator buttons on both left and right, plus another button on the right to cancel the flashing. (Somehow that system stayed in place for many years.) The RS also lost points with some riders for its tall seat, which was usefully broad but combined with the bike's substantial weight (252 kg with five litres of fuel) to make it a bit unwieldy at low speed.
Even so, I didn't have too many problems manoeuvring the BeeEm through light traffic, helped by its injection system's crisp response and the generous low-rev delivery. I wasn't particularly impressed by the whirring and whistling sounds coming from the liquid-cooled engine and the rather ugly stainless-steel four-into-one exhaust system, but it was easy to understand why the RS had inspired such enthusiasm among testers when new. ‘Its power delivery is superb,' one wrote. ‘You can idle along in fifth at less than 2,000 rpm and then power away without a hiccough from 25 mph to 130 mph [40 to 210 km/h]. Hang on to third or fourth gear at over 6,000 rpm and the motor really flies.'
That was certainly still true of this sweet-running machine. When I reached that first stretch of dual-carriageway, I accelerated through the box until I was doing just over 160 km/h in top, then settled back to a 140-km/h cruise that brought those memories of my original test flooding back. At that speed, the RS felt utterly relaxed. The slight
buzz at most engine speeds, typical of the K-series fours, was noticeable but not annoying.
Despite its respectable maximum of about 210 km/h, the RS couldn't keep up with those Japanese rivals in top-end acceleration or outright speed, but its flexibility made the bike respectably rapid in many roadgoing conditions. Although outclassed in standing quarter-mile acceleration, it beat both the GPZ and FJ1100 over the quarter mile in a top-gear roll-on test from 80 km/h. It was also the most economical on fuel, which helped its rider obtain a useful range from the 22-litre tank before the first of two warning lights came on.
Handling was very acceptable, too, provided you didn't expect sports-bike agility and could put up with the soft front forks, which made the front end dive when Brembo's powerful twin-disc brake was used hard. The narrow handlebars, combined with the bike's weight, old-fashioned steering geometry, 18-inch front wheel (defiantly untrendy, when most Japanese rivals were following grand prix fashion with 16-inchers), and long wheelbase made the RS quite hard work on twisty back roads.
But more open roads were a different and much more positive story. High-speed stability was excellent, the steering had a pleasantly neutral feel and, provided I didn't get too aggressive, the BMW was very enjoyable to ride. There was enough ground clearance to make good use of the grip of its Avon Super Venoms. I could even understand how one tester had raved: ‘With its seeming lack of weight or obtrusive bulk, the RS simply flows round bends. Flicking it through the twists and turns… will convince you that it is, quite simply, superior.'
Well, maybe. The BMW's more compliant suspension certainly gave a more comfortable ride than that of most contemporary rivals and comfort levels were also boosted by its cleverly designed fairing. The top section combined a usefully tall, lipped screen with large mirrors that also held the indicators and diverted the wind around the rider's hands. (Heated grips were an option.) The lower section ended above the sticking-out engine, which contributed useful lower leg protection.
The RS' seat was generally reckoned to be more comfortable that the one that I'd found painfully firm when testing the naked K100 back in 1984. This time round I didn't ride far enough to be sure, but the BMW felt very promising. So capable, long-legged, and effortlessly powerful, in fact, that it felt ready to be aimed at some distant location, with no need for any preparation other than topping up the tank, checking oil and air, then fitting and filling the accessory panniers.
Those panniers were criticised for flimsy hinges, but they mounted easily and were typical of the RS' high level of equipment, which also included an excellent tool-kit. The RS was expensive (£4,290, that is, Rs 3.86 lakh, in the UK, compared to the GPZ900R's £3,199, that is, Rs 2.88 lakh) but it was a serious piece of kit. ‘The way I could slip into its comfortable riding position and reel off a quick 300 miles (483 km) without feeling tired had warmed me to the essentially practical nature of the RS,' as a contemporary tester put it. ‘It's no poser's toy, but a complete package for the serious motorcyclist willing to pay for such a skilful blending of the right ingredients.'
It's easy to understand that enthusiasm when you ride a bike as good as this one. Few other 1980s machines would inspire such confidence or generate such enthusiasm for a long trip and I was glad to have had the opportunity to ride the BMW again. My memories of the RS on that Isle of Man test were mixed, to say the least. But all these years later I was seriously impressed by the bike that led BMW's multi-cylinder revolution.