BMW K1200S

The BMW K1200S is perhaps the most significant new model from the German factory in the last 20 years. Four cylinders, electronic suspension adjustment, 180mph performance – this is the new territory for BMW.

Can they cut it in the white-hot sportbike sector of the market? Time will tell, but Roland Brown reckons they´ve got a very strong chance indeed.

The guy on the blue-and-white K1200S flashed past me while I was cruising along in relaxed fashion on an identical bike, enjoying the view of the spectacular Alpine scenery near the German-Austrian border. This rider was quick and neat, and looked as though he knew where he was going. If I was going to keep up and follow him, I couldn´t afford to delay.

With my left thumb, I pressed a round button on the BMW´s handlebar to activate the electronic suspension adjustment, then jabbed it twice more to change the front and rear shock setting from Comfort to Sports mode, firming up the damping. Then I wound back the throttle, and held on tight as the four-cylinder engine punched the bike forward.

For the next few miles it was a memorable ride. I screamed the bike through its six-speed gearbox on the straights, and tipped it hard into the many tight bends behind a similarly angled bike whose rider´s knee occasionally brushed the ground. Occasionally we slowed for a village, before immediately regaining the pace once again on the exit.

Finally, after about 20 minutes, we reached a junction, and both realised that in the rush we had missed a turning some way back. By the time we had retraced our route, the riders behind us had all gone ahead. But the high-speed chase had been worthwhile as well as fun, because it had highlighted the speed and stability of the K1200S.

Not that there had been any doubt beforehand that this bike is something special. Its sleek shape, 165bhp power output and dry weight of 227kg also confirm that the K1200S is not just the fastest ever BMW, it is also by a long way the most sporty and aggressive. It is one of the most technically innovative, too, with its non-telescopic front suspension system, based on the design developed by British engineer Norman Hossack in the 1980s.

The reasoning behind the 1200S´s arrival had become clear at the previous evening´s technical presentation, with the words of BMW board member Ernst Baumann. ‘The world bike market is developing only at a moderate rate, and in Germany the market has declined over the last five years,’ he said. ‘So for us, significant growth is only possible if we move into new areas. The S is one brick in our attack – a move towards more performance.’

That they have discovered a lot more performance was confirmed the following morning, after we´d set out from the launch base near BMW´s Munich headquarters. Even lined up at a standstill before we left, the S-bikes had looked notably leaner and more sporty than traditional K-models, with a sharp nose to the full fairing. The riding position is sporty without being radical, thanks to reasonably low-set footrests.

ENGINEERING AT SPEED

The new transverse four-cylinder motor, its cylinders angled forward at 55 degrees, fired up with a pleasing rasp through its huge silencer on the right side. The bike felt light and low (seat is 820mm high, with a 30mm lower one available as a no-cost option). But after pulling away I was less impressed by the low-rev performance of the fuel-injection system, which coughed slightly before clearing at about 4000rpm. This was mildly annoying: nowhere near as bad as Triumph´s TT600 was on its debut a few years ago, but a surprise all the same.

Minutes later, low-rev response was forgotten because I was on an autobahn, where the big four shot forward smoothly, and sat at an effortless indicated 90mph, its rider reasonably well protected by the fairing and low but fairly wide, non-adjustable screen. With no speed limit to worry about, the temptation to stretch the BMW´s legs was irresistible, and the bike was happy to oblige.

Power was delivered in a very linear, seamless way, and the 1200S revved smoothly and rapidly through the gears, effortlessly topping 140mph given just a few seconds´ flat-out acceleration, while I tried to tuck down despite the handicap of a tank-bag. Given enough room, the BMW makes enough power to show over 175mph on its white-faced analogue speedometer. I and most other testers I spoke to also found the bike very stable, although one rider reported a weave at close to the top speed.

More importantly there was also enough midrange power to make for instant overtaking urge. The response to a top-gear twist of the wrist from 70mph was pretty strong, though the BMW couldn´t match the grunt of Honda´s Blackbird or Suzuki´s Hayabusa. That meant I required slightly more frequent use of the six-speed gearbox, which I found good but not as sweet as some. A few riders were more critical, complaining of a notchy feel and missed shifts.

Comfort at high speed was also pretty good, with reasonable wind protection, a broad seat and roomy riding position. The mirrors were excellent, too. Thanks to its twin balancer shafts the four was generally smooth, with just enough buzz at most engine speeds to let you know it was running. But the more noticeable tingle at around 6000rpm made my hands slightly numb after sitting at 90mph behind the photographer´s car for half an hour.

Fortunately that was soon forgotten when we turned off onto twisty roads on which I could explore the BMW´s handling. This lived up to expectations, though before marking the K1200S as a sports bike and expecting it to compete with the latest open-class race-replicas, it´s important to remember that at 227kg dry this bike weighs almost 50kg more than a GSX-R1000, for example, is far longer, and is a much more natural competitor for the Hayabusa.

The BMW´s non-telescopic front suspension system worked well, giving a reasonably comfortable ride, yet maintaining excellent stability even under hard braking. The Hossack system has been engineered to give a slight downward movement under braking, but scores over conventional telescopic systems because its single, central spring does not automatically compress under braking, so the suspension unit can continue working properly, even as the bike is braked deep into a corner.

The S-bikes on the launch were also all fitted with an optional extra, BMW´s Electronic Suspension Adjustment (or ESA). Using small electronic motors linked to the hydraulic systems of both front and rear WP shock units, ESA allows the rider to adjust front and rear spring preload and damping.

Preload adjustment must be done at a standstill: just press the ESA button, then press and hold it again to toggle between Solo, Solo with luggage or Two-up modes, the chosen setting being shown by a diagram in the digital instrument panel. Pressing the same button quickly, with the bike either stationary or moving, toggles damping between three settings for Comfort, Normal or Sports. Front and rear are adjusted together; rebound damping only at the front, and both compression and rebound at the rear.

It´s an excellent idea, and well implemented. Being quite heavy, I put the preload on the middle setting, and changed damping on the move, according to how bumpy the road was and how hard I was riding. The differences were noticeable and worthwhile. Being able to add damping without even stopping was a real bonus, especially when that rider came whistling past, and I suddenly wanted to speed up.

During that chase, the BMW´s stability was impressive both under braking and acceleration. And although it didn´t approach the agility of a much lighter super-sports bike, the aluminium-framed BMW steered reasonably quickly despite its length, and could be flicked through tight bends with minimal effort. On these roads ground clearance wasn´t a problem, and the Metzeler Sportec M-1 rubber, the rear a fat 190-section radial on a six-inch rim, were well up to the job.

There was also no doubting the power of the 1200S´s brake system, which combines 320mm front discs and four-piston Brembo calipers with a variation on BMW´s servo-assisted EVO system. Squeezing the handlebar lever operates both front and rear brakes, but the foot pedal works only the rear disc. The test-bikes were also fitted with ABS, listed as standard although the bike is available without.

Most of the time the system worked well, giving very sharp stopping via the front discs, with a little worthwhile help from the rear. Whether the servo affect is necessary on a bike of this relatively light weight, though, I´m not so sure, as the trade-off is a very slight loss of sensitivity, compared to the direct feel of a standard double-disc front brake.

AN OOPS TYPE MOMENT

My real problem, though, came when I braked hard into a sharp, downhill right-hand bend. I thought I´d left sufficient room to slow for the turn, until suddenly the ABS cut in unexpectedly, causing the bike to surge forward and arrive at the bend too fast. Rather than attempt to make the turn, I opted to keep braking hard in a straight line, using the empty opposite side of the road. But I hadn´t quite managed to stop when the front wheel hit the kerb, puncturing the tyre and snapping one of the suspension linkages.

The accident was obviously due at least partly to my leaving my braking too late for the bend. But there was nothing particularly slippery on the road, and I´m sure I´d have stopped in time on a bike without ABS, which (in combination with this front suspension system) seemed to struggle when faced by hard braking on a steep downhill gradient. If I were buying a K1200S I´d be tempted to save some money by specifying a non-ABS model, which costs £9750 compared to the ABS bike´s £10,545 on the road. On the other hand the ESA is good value at £430, especially for anyone who carries a pillion or luggage.

The 1200S also has some other neat details, including its light and attractive cast wheels, the front of which locates its tyre valve very accessibly on a spoke. The lightweight shaft drive system, similar to that of the R1200GS, is neatly designed, too. I was less impressed by the dated looking instrument console, which combines a small digital display with analogue speedo and tacho. The digital fuel gauge was pessimistic, saying the 19-litre tank was almost empty after just 110 miles, when in fact it took only 14 litres.

Fuel range is arguably less important with this bike than with any previous large-capacity BMW. It´s seriously fast, handles very well, and has a notably sharper, more aggressive image than previous K-series machines. But despite its name and nature, this radical new four-cylinder machine is more of a BMW than I´d expected; as much an all-rounder as a sports bike.

The K1200S is striking, innovative and crammed with technology, though slightly rough round the edges in places. Riders moving from previous K-series BMWs will probably love it, but the S-bike´s success depends on enough people making the switch from rival marques. Whether that happens remains to be seen. What´s for sure is that the K1200S is good enough to give Super Blackbird, Hayabusa and ZX-12R riders, in particular, a serious alternative.

THE MAKING OF THE MOTOR

The key feature of the 1157cc four-cylinder engine was BMW´s decision to angle the cylinders at 55 degrees from vertical, in order to keep the centre of gravity as low as possible. This inevitably leads to a relatively long wheelbase (the K12´s is 1571mm, compared to the Yamaha R1´s 1395mm) but has the benefit of putting much weight on the front wheel, and also leaving space above the engine for an efficient intake system.

BMW´s engineers called on the firm´s Formula One race car engine experience to design a dohc, 16-valve powerplant with oversquare dimensions of 79 x 59mm, and cams situated directly above the valves, and opening them via follower arms in typical F1 style. Valve angle is a notably steep 10 degrees intake, 11 degrees exhaust. The exhaust cam is driven by chain from the crankshaft, and turns the inlet cam by gear, which helps make for a compact cylinder head.

At 13:1, compression ratio is higher than the Japanese litre engines, an indication of efficient combustion. The rev limit is 11,000rpm, although BMW claims the components could withstand much higher revs. A sequential fuel-injection system, incorporating anti-knock technology and a ram-air effect from the twin intakes either side of the headlight, help give a peak power output of 167bhp at 10,250rpm. The maximum torque figure of 130N.m (96lb.ft) arrives at 8250rpm. The 4-2-1 exhaust system incorporates a stainless steel silencer and three-way catalytic converter.

More Formula One ideas have been used in the bottom-end, where the one-piece forged crankshaft is fed oil directly in an axial flow, and from there via holes in the crankshaft to the conrod bearings (instead of via the crankcase to the main bearings and on to the conrod bearings, in conventional fashion). This allows a very short crank, and minimum gap between cylinders. BMW says the 1200 S engine´s width of 430mm at crankshaft level is closer to a typical 600cc four than a 1000cc plus engine.

Other notable bottom-end features are the dry sump lubrication system, chosen because it gives a steady flow under all conditions, and allows the motor to be held lower. (Oil lives in the frame triangle behind the engine.) Twin balancer shafts, located below the crank, control the straight-four motor´s secondary vibration. The alternator and starter are positioned behind the crankshaft in the space above the gearbox.

The six-speed gearbox is a cassette type, which along with theoretical ease of changing ratios (hardly vital for this bike) gives an assembly advantage by allowing the whole box to be pre-assembled. Unlike all BMW´s previous shaft-drive engines, this one uses an integrated gearbox unit, and wet multiplate clutch, instead of the previous and bulkier dry, single-plate clutch.

BMW had no intention of abandoning shaft final drive even for this bike, despite having to turn the drive from the crankshaft through 90 degrees. Particularly as the firm claims that the power loss is only a few per cent, and that a drive chain becomes less efficient after a certain degree of wear, while the shaft maintains its efficiency.

The aluminium Paralever swing-arm pivots in a new position below the drive shaft´s front universal joint, and is designed to avoid changes of length with rear suspension movement. The shaft´s aluminium final drive housing is similar to that of the R1200 GS, being filled with oil for life, and featuring a 50mm hollow axle tube that is designed to aid heat dissipation.

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