BMW K Series. February 2009
BMW Motorrad is now entering the 26th year of production of the K Series. We follow the rise, and rise of this popular model.
The Inline-engine BMW
Since commencing to build motorcycles, BMW had kept to the concept of the flat-twin engine, unit gearbox and shaft drive. While this package had proved successful, by the 1980s BMW were falling behind the market in terms of performance. They needed a new bike to retain the intrinsic image and style of the BMW, but deliver greater performance. The answer was the K Series, which was launched late in 1983 as the basic K100, the K1000RS with sports fairing, and was followed later by the K100RT tourer.
Essentially one engine design was utilised with minor variations. The engine hung from a tubular frame, suspension was by telescopic front and monolever rear. The arrival of the K Series resulted in the R100 models being dropped early in 1984The K Series engine was a 987cc straight four power unit fitted in longitudinal, flat configuration. The crankshaft was on the right hand side seen in the direction of travel, while the cylinder head with the two overhead camshaft was on the left. Liquid cooling came for the first time on this new BMW, ensuring not only thermal stability, but also, through efficient soundproofing, a very low level of mechanical noise.
Two other innovations likewise characterised the new engine. First, electronic fuel injection supplying fuel to the combustion chambers. Second, the layout of the engine as a load bearing element fully integrated in the light and torsionally stiff tubular steel spaceframe. This principle set the foundation for the BMW K-Series motor-cycles. So regardless of whether they are Sports Machines, Tourers or Naked Bikes - the K-Series proves to be extremely innovative and versatile in tech-nical terms and virtually every other respect. To this day, the concept of the straight-four fitted lengthwise remains within the BMW Motorrad model range in the guise of the K 1200 LT Luxury Tourer.
Ongoing development of the K-Series also provides important momentum for a brand new technical approach. In 2004, for example, the first BMW K Series with its four-cylinder engine fitted crosswise saw the light of day - the K 1200 S as the most powerful and fastest BMW of all times. Just how much development margin and what a great potential this new concept offers in the K-Series is subsequently borne out not only by the new K 1200 R high performance Roadster based on the new sports model, but also by the K 1200 GT High Performance Tourer.
Increasing engine size on these models and introducing new, innovative solutions, BMW Motorrad is now opening up another, definitely equally successful chapter in the history of the Company's K models. The Two-Valve Models as of 1983 K 100 (1983-1990).The K 100 launched in 1983 - exactly six decades after the launch of the very first BMW motorcycle with its Boxer engine - is BMW's first production model with a four-cylinder power unit. But instead of following the usual Japanese concept with the straight four engine fitted crosswise, BMW once again takes a new and unusual approach: Featuring liquid-cooling and not air-cooling like most other production motorcycles, the four-cylinder power unit is fitted flat in longitudinal direction as a load-bearing element in the tubular steel spaceframe, with the transmission of power from the gearbox to the rear wheel through a drive shaft. The K 100 is one of the first production motorcycles in the world to feature fuel injection (Bosch LE-Jetronic) supplying the fuel/air mixture to the 987cc four cylinder with two valve operated cup tappets per cylinder.
Two other innovations in the production of BMW series machines are the two overhead camshafts as well as the Monolever single swing arm on these dynamic 1000cc models. BMW's first ever four-cylinder is upgraded in 1987, a freestanding headlight taking the place of the former headlight/instrument unit, a black painted engine and painted rims as well as a dynamic style fuel tank/seat combination marking the most important differences. As before, engine output is 90 hp at 8,000 rpm. K 100 RS (1983-1989). Introducing the K 100 RS, BMW adds a sports model to the existing range with the same engine and suspension technology, but now featuring a carefully designed aerodynamic fairing. The handlebar fitted lower down provides a more sporting seat position, the fairing carefully developed in the wind tunnel, together with its adjustable wind deflector and the direction indicators integrated in the rear mirrors, combining a sporting look for high speeds with all the grand touring comfort so typical of a BMW.
For a long time the K 100 RS remained the ideal synthesis of sportiness and touring comfort and, with a production run of more than 34,000 units, becoming the best selling model in the first generation of the K-Series. BMW offered the K 100 RS as well as the other four-cylinder models in the K-Series as of 1988 with ABS as a special feature. K 100 RT (1984-1989).In 1984 BMW Motorrad launched the ultimate Grand Touring Machine, the K 100 RT based on the K 100 RS. Featuring the same engine and suspension technology as the RS, this new model combined a sporting and dynamic style of riding with protection from wind and weather on long distances provided by the higher and wider full fairing. K 100 LT (1986-1991).In 1986 BMW launched a luxury version of the successful K 100 RT, the new K 100 LT. The Grand Touring machine also featured a generously upholstered comfort seat, a radio, topcase and special paintwork, that saw the K 100 LT soon outsell the K 100 RT "basic" model in the market. The new machine left virtually nothing to be desired in terms of comfort and features, making this Luxury Tourer the role model for a whole new generation of extravagant touring machines. K 75 C/K 75 (1985 - 1996).
Two years after the launch of the K-Series with its four-cylinder power unit, BMW broadened the new product line through the introduction of the K 75 C with a straight three engine. While the suspension and running gear is based almost entirely on the technology of the large four cylinder, the 740cc power unit is a new construction. Again fitted lengthwise and in flat arrangement as a load bearing element in the space frame, this liquid-cooled three cylinder with 67 millimetres/2.63"cylinder bore and 70mm/2.76"stroke came with the same basic specifications as the larger K 100. The drive shaft positioned beneath the crankshaft gave the three cylinder particular smoothness and refinement also thanks to the balance weights used on the shaft. Developing maximum output of 75hp on total weight with a full tank of 227 kg/501 lb, the K 75 C stands out above all as a particularly agile motorcycle for country roads. One year after the launch of the K 75, the customer was given the choice of a new alternative, the K 75 C with its cockpit fairing fitted firmly to the handlebar.
Now the headlight and instruments were no longer integrated into the cockpit fairing, but rather stood out freely on the machine, with the rear drum brake in combination with the 18-inch rear wheel being replaced as of 1990 by a disc brake and a 17-inch rear wheel. The engine was finished in black and the fuel tank/seat combination served to further upgrade the K 75. Accounting for approximately 28,000 units, the two "basic" versions of the K 75 became the most successful representatives of their model series.K 75 S (1985-1995).Introducing the K 75 S, BMW added a sporting sister model to the K 75 C. While the suspension and drivetrain were based on the K 75 C, the slender semi shell bearing fitted firmly to the frame revealing the sporting character of the motorcycle.
The K 75 S also came with a firmer spring/damper set-up featuring shorter spring travel and a 17-inch rear wheel with a disc brake instead of the full hub drum brake on the basic model. The K 75 S Special launched in 1986 boasted an engine spoiler introduced as a standard feature in 1988. As of 1990 the K 75 S, like all other three-cylinders, is available with ABS. And starting in the 1991 model year, three-spoke light alloy wheels took the place of the eight-spoke cast wheels used so far.K 75 RT (1989-1996).In 1989 BMW carried over the successful concept of the K 100 RT to the three-cylinder model series, thus creating the K 75 RT. On this new model the aero-dynamic full fairing offered protection from wind and weather on long distances, while the wide range of optional extras and special equipment left nothing to be desired.
On 18 March 1991 the one millionth model built by BMW Motorrad - a K 75 RT - came off the production line. Introducing two special models, the K 75 RT Ultima and the K 75 Ultima, each in special paintwork, with ABS, a catalytic converter and case holders, BMW finally ceased production of the three-cylinder model series in the Summer of 1996 after a total production volume of the K 75 amounting to 68,011 units.The First Generation Four-Valve ModelsK1 (1988-1993).In 1988 the K1 set another milestone in the history of the BMW K-Series. Apart from its brand new design and aerodynamics concept, the K1 is BMW's first production motorcycle with four-valve technology, small valve angles, and extremely advanced design of the combustion chambers. The greater cylinder charge achieved in this way was reflected by the extra power of the engine, the K1 developing maximum output of 100hp at 8,000 rpm - more than any other BMW before. Featuring new Bosch Motronic fuel injection, 17-inch wheels and ABS, the K1 also set new highlights in technology, one example being the Paralever double joint rear wheel swing arm introduced a year before on the R 100 GS and effectively preventing drive forces from the drive shaft and any undesired effects of this kind on the rear wheel suspension. The K1 was also the world's first production machine to feature a fully controlled three way catalytic converter, which has subsequently been introduced on all BMW motorcycles as of 1991.
Production of the K1 ended in 1993 with the special Ultima model. K 100 RS (1989-1992).The innovative four-valve tech-nology introduced on the K1 with its engine output of 100hp made its way back into the market in 1989 in the highly successful K 100 RS. While the combination of the fuel tank and seat as well as the fairing with direction indicators integrated in the rear-view mirrors corresponds to the former model, the new K 100 RS, like the K1, benefited from new 17-inch wheels, larger brakes, and the Paralever single swing arm at the rear.K 1100 LT (1991-1999).
In 1991 BMW reached another milestone in the history of the K-Series through the introduction of the K 1100 LT, the first BMW to displace more than 1,000cc, an increase in cylinder bore from 67 to 70.5mm giving the engine 105 cc more capacity, the upgraded K four-cylinder developing maximum output of 100hp from 1,092cc at an engine speed of 7500 rpm. A factor far more important on the road than the increase in maximum output by 10hp over the former model was the increase in torque. Offering a lot more traction and pulling power, the K 1100 LT was a real performer in the Luxury Tourer market. Another important feature offered by the K 1100 LT for the first time was the electrically adjustable windshield. Newly developed cases and a special topcase, finally, rounded off the range of touring features. Launching the K 1100 LT Highline in 1997, BMW Motorrad introduced a special model highlighting the luxurious claim of this supreme Tourer by sophisticated chrome components and equally outstanding special paintwork.K 1100 RS (1992-1996).Just one year after introduction of the large four-cylinder in the K 1100 LT, the same 100hp power unit was featured in the LT's sporting sister model, the K 1100 RS.
The newly designed fairing with its lower section encompassing the engine ensured even better aerodynamic qualities and once again optimised the protection of wind and weather. A new Marzocchi telescopic fork as well as the firmer suspension set-up gave this sporting all rounder even greater dynamic qualities.
A particularly sophisticated special model, the K 1100 RS with its polished immersion tube, black painted tank and upper fairing, as well as distinctive elements finished in silver such as the cooling air intake, the lower section of the fairing and the rear fairing, gave this special model a very particular touch. K 1200 RS (1996-2005).The K 1200 RS launched in Autumn 1996 took yet another step in terms of engine size and driving dynamics. A new crankshaft now offering 75 instead of 70mm stroke, increasing engine capacity by exactly 79cc to 1171cc, with power up from 100 to 130hp at 8,750 rpm. The new six-speed gearbox ensured even more dynamic performance and the new suspension reflected the sporting style of this new top end model. For the first time the K 1200 RS featured a light alloy bridge frame integrating the four-cylinder power unit no longer as a load-bearing element, but rather as a detached unit not conveying any vibration to the machine. The K 1200 RS was the first model in the K-Series to feature the unique front wheel Telelever originally introduced on the R 1100 RS in 1993. K 1200 LT (1998-2008).Two years after the introduction of the K 1200 RS, BMW presented a particularly luxurious Tourer in the guise of the K 1200 LT. Based on the suspension and engine technology of the K 1200 RS, the K 1200 LT also featured a new light alloy bridge frame as well as an increase in capacity to 1,171cc. Offering maximum output of 98hp at just 6,750 rpm and peak torque of 115Nm at a low 4,750 rpm, the K 1200 LT was designed less for peak performance rather than for supreme torque and pulling power. Hence, it only needed a five-speed gearbox for superior touring in genuine style. Apart from the full fairing offering perfect protection from wind and weather, as well as cases integrated in the overall design and layout of the machine and a topcase offering a total capacity of 120-litres, the K 1200 LT, with its HiFi player, on board computer, cruise control, heated handles and optionally heated seat offered touring comfort of a standard never seen before.
The K 1200 LT was further upgraded in the 2004 model year, now benefiting from an even more powerful engine with 116hp and 120Nm maximum torque, an electro-hydraulically activated main stand and a rear spring element with travel dependent damping. To this day, the K 1200 LT comes right at the top of this market segment.K 1200 GT (2002-2005).The K 1200 GT made its debut in 2002 as an enhanced variant of the K 1200 RS giving even greater emphasis to touring comfort. Boasting 130hp maximum output, featuring a higher windshield and handlebar, optimised seating comfort and a case system fitted as standard, the K 1200 GT was even more of a genuine Gran Turismo, redefining supreme touring comfort. The full fairing ensured not only optimum protection from weather, but also, in conjunction with a powerful engine, guaranteed high average speeds on long distances. The Second Generation of Four-Cylinders K 1200 S (2004-2008).The K 1200 S made its entry into the market in 2004 as a radically new and highly innovative sports machine standing out as a unique model within the K family. With its new straight four now fitted crosswise and displacing 1,157cc, the K 1200 S has no predecessor and no role model in the history of BMW Motorrad. The technical highlights of this 16-hp sports machine are the very sloped angle of the cylinder bank tilted 55° to the front to provide a low centre of gravity as well as innovative suspension technology with the BMW EVO Paralever and the BMW Duolever at the front. On the BMW Duolever, the square set-up of arms consisting of two longitudinal arms pivoting within the frame guides the wheel bearings and thus allows appropriate wheel travel.
The K 1200 S combines supreme riding precision and agility with a standard of engine power and riding performance that leaves nothing to be desired. As an option BMW even offered Electronic Suspension Adjustment on the K 1200 S for the first time in series production. This allows the rider to adjust the suspension and damping individually to his personal style and the load the machine is carrying.K 1200 R (2004-2008).Launching the high performance K 1200 R Roadster, BMW entered the segment of high power Naked Bikes for the first time in 2004. Based on the K 1200 S, the new K 1200 R benefited from the straight four engine with dry sump lubrication as well as innovative suspension technology. Developing 163hp at 10,250 rpm, the K 1200 R is almost as powerful as the sports model with its special fairing, immediately moving to the top in the Naked Bikes segment. The new Roadster also bears out its superior performance through the special look of this new machine.
Special body elements around the tank and rear end as well as the striking dual headlight with its surface finished in matt chrome particularly stand out. Fitted with racing tyres, carbon trim and other motorsport components, the K 1200 R was an impressive new addition to the K family. K 1200 GT (2006-2008).Following the success of its predecessor of the same name, the K 1200 GT opened up new dimension in riding dynamics and long distance touring in 2006, combining maximum agility and dynamics in an overall package equally well suited for superior touring. To reach this objective the development engineers at BMW Motorrad carried over the suspension and engine technology of the K 1200 S into this new Sports Tourer.
The new machine is powered by BMW Motorrad's modern straight four power unit fitted crosswise in the machine and developing 152hp in the GT version.With its semi-fairing bolted firmly on to the frame, the headlight unit carried over from the R 1200 S and its handlebar detached to prevent the transmission of vibrations, the K 1200 R Sport from BMW Motorrad is positioned between the naked K 1200 R and the fully fairing K 1200 S.In the style of a genuine Naked Bike, the K 1200 R Sport offers a free view of the impressive suspension and engine components. And at the same time the range of practical use provided by the new machine is much larger than before, significantly better wind protection allowing the rider to cover longer distances at a high speed, while the upright seating position and the wide handlebar guarantee maximum agility on sporting country roads and tours.