The Inline-Engine BMW.
Back in 1983, when many motorcycle manufacturers still placed their bets on inline engines with air cooling, liquid-cooled four-cylinder power units marked the highest level of technology in motorcycle construction. But instead of resorting to the usual engine layouts, BMW engineers Josef Fritzenwenger and Stefan Pachernegg succeeded in developing a brand-new future-oriented technical concept subsequently enhanced all the way to regular production quality.
In the process they maintained the longitudinal position of the crankshaft typical up to that time of BMW motorcycles with a direct flow of power from the gearbox through the drive shaft to the rear wheel, referred to under the official term as the BMW Compact Drive System. A brand-new approach, on the other hand, was the introduction of liquid cooling.
Displacing 987 cc, the straight-four power unit is fitted in longitudinal, flat configuration. The crankshaft is on the right-hand side seen in the direction of travel, while the cylinder head with the two overhead camshaft is on the left.
Liquid cooling comes for the first time on this new BMW, ensuring not only supreme 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 sets the foundation for the BMW K-Series motorcycles. So regardless of whether they are Sports Machines, Tourers or Naked Bikes - the K-Series proves to be extremely innovative and versatile in technical 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 sees 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 fl at 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 remaining in a technology so typical and well-proven at BMW: 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 987-cc 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 1000-cc models.
BMW's first-ever four-cylinder is upgraded in 1987, a free-standing headlight taking the place of the former headlight/instrument unit, a black-painted engine and painted rims as well as a dynamically 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 remains the ideal synthesis of sportiness and touring comfort and, with a production run of more than 34,000 units, becomes the best-selling model in the first generation of the K-Series. BMW offers 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, thus taking on the leading role in introducing this technology in the motorcycle world.
K 100 RT (1984-1989).
In 1984 BMW Motorrad launches 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 combines a sporting and dynamic style of riding with perfect protection from wind and weather on long distances provided by the higher and wider full fairing. The comfortable seating position enjoyed by both the rider and pillion as well as a wide range of BMW options and special equipment comprising, for example, baggage cases, a tank rucksack or heated handles, quickly make the K 100 RT the benchmark in its segment.
K 100 LT (1986-1991).
In 1986 BMW launches a luxury version of the successful K 100 RT, the new K 100 LT. The response to this Grand Touring machine also featuring a generously upholstered comfort seat, a radio, topcase and special paintwork is so overwhelming that the K 100 LT soon outsells the K 100 RT "basic" model in the market.
The new machine leaves 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 broadens 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 innovative technology of the large four-cylinder, the 740-cc power unit is a brand-new construction nevertheless following the basic layout of the four-cylinder very closely indeed.
Again fitted lengthwise and in fl at arrangement as a load-bearing element in the spaceframe, this liquid-cooled three-cylinder with 67 millimetres/2.63"cylinder bore and 70 millimetres/2.76"stroke comes with the same basic specifications as the larger K 100.
The drive shaft positioned beneath the crankshaft gives the three-cylinder particular smoothness and refinement also thanks to the balance weights used on the shaft. Developing maximum output of 75 hp 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, without requiring the rider to give up the grand touring comfort so typical of a BMW.
Just one year after the launch of the K 75, the customer is 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 are now longer integrated in the cockpit fairing, but rather stand 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 finished in black and the dynamically designed fuel tank/seat combination serve to further upgrade the K 75. Accounting for approximately 28,000 units, the two "basic" versions of the K 75 become the most successful representatives of their model series.
K 75 S (1985-1995).
Introducing the K 75 S, BMW adds a sporting sister model to the K 75 C. While the suspension and drivetrain are based on the innovative technology of the K 75 C, the slender semi-shell bearing fitted firmly to the frame clearly reveals the sporting character of the motorcycle right from the beginning.
The K 75 S therefore also comes 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 boasts an engine spoiler introduced as a standard feature in 1988.
As of 1990 the K 75 S, like all other three-cylinders, is likewise available with ABS. And starting in the 1991 model year, three-spoke light-alloy wheels take the place of the eight-spoke cast wheels used so far.
K 75 RT (1989-1996).
In 1989 BMW carries 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 sophisticated aerodynamic full fairing offers outstanding protection from wind and weather on long distances, while the wide range of optional extras and special equipment so typical of BMW leaves nothing to be desired also on the Tourer with its three-cylinder power unit.
On 18 March 1991 a K 75 RT comes off the production lines at BMW as the one-millionth model built by BMW Motorrad.
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 ceases production of the three-cylinder model series in summer 1996 after a total production volume of the K 75 amounting to 68, 011 units.
The First-Generation Four-Valve Models
In 1988 the K1 sets another milestone in the history of the BMW K-Series. Apart from its brand-new design and aerodynamics concept remaining unique in the motorcycle world to this day, 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 is reflected by the extra power of the engine, the K1 developing maximum output of 100 hp at 8, 000 rpm - more than any other BMW before.
Featuring new Bosch Motronic fuel injection, 17-inch wheels and ABS, the K1 also sets 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 is also the world's first production machine to feature a fully-controlled three-way catalytic converter, making a significant contribution to environmental protection and subsequently introduced step-by-step on all BMW motorcycles as of 1991.
Production of the K1 ends in 1993 with the special Ultima model.
K 100 RS (1989-1992).
The innovative four-valve technology introduced on the K1 with its engine output of 100 hp makes 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, benefits form new 17-inch wheels, larger brakes, and the Paralever single-swing arm at the rear.
K 1100 LT (1991-1999).
In 1991 BMW presents yet another milestone in the history of the K-Series through the introduction of the K 1100 LT, the first BMW to displace more than 1,000 cc: an increase in cylinder bore from 67 to 70.5 millimetres (2.63 to 2.78") gives the engine 105 cc more capacity, the upgraded K four-cylinder developing maximum output of 100hp from 1,092 cc at an engine speed of only 7,500rpm. four-cylinder developing maximum output of 100 hp from 1,092 cc at an engine speed of only 7,500 rpm.
A factor far more important on the road than the increase in maximum output by 10 hp over the former model is the significant increase in torque. Offering a lot more traction and pulling power, the K 1100 LT is even more superior on the road and for a long time represents the topmost level in the Luxury Tourer market. This is also borne out clearly by the fundamentally upgraded suspension with its Paralever single-swing arm effectively keeping out any undesired disturbance from the drivetrain and thus ensuring even greater comfort and riding smoothness.
Another important feature offered by the K 1100 LT for the first time is the electrically adjustable windshield. Newly developed cases and a special topcase, finally, round off the well-conceived range of touring features again so typical of BMW.
Launching the K 1100 LT Highline in 1997, BMW Motorrad introduces 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 100-hp power unit is featured in the LT's sporting sister model, the K 1100 RS. The newly designed fairing with its lower section encompassing the engine ensures even better aerodynamic qualities and once again optimises the protection of wind and weather so typical of BMW.
A new Marzocchi telescopic fork as well as the firmer suspension set-up gives 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, give this special model a very particular touch.
K 1200 RS (1996-2005).
The K 1200 RS launched in autumn 1996 takes yet another step in terms of engine size and driving dynamics. A new crankshaft now offering 75 instead of 70 millimetres (2.95 instead of 2.75") stroke increases engine capacity by exactly 79 cc to 1,171 cc, with power up from 100 to 130 hp at 8,750 rpm.
The new six-speed gearbox ensures even more dynamic performance and the brand-new suspension clearly reflects the sporting style of this new top-end model.
For the first time the K 1200 RS features 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 is the first model in the K-Series to feature the unique frontwheel Telelever originally introduced on the R 1100 RS in 1993. Individual ergonomic preferences, finally, are taken into account by the option to adjust the handlebar, the windshield, the footrests and the seat (for height).
K 1200 LT (1998-2008).
Two years after the introduction of the K 1200 RS, BMW presents a particularly luxurious Tourer in the guise of the K 1200 LT, leaving all conventional standards and models far behind. Based on the suspension and engine technology of the K 1200 RS, the K 1200 LT also features a new light-alloy bridge frame as well as an increase in capacity to 1,171 cc.
Offering maximum output of 98 hp at just 6,750 rpm and peak torque of 115 Newton-metres (85 lb-ft) at a low 4,750 rpm, the K 1200 LT is designed less for peak performance than rather for supreme torque and pulling power. Hence, it only needs 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 offers touring comfort of a standard never seen before.
This wide range of equipment explains the signficant overall weight of 378 kg or 833 lb, which BMW also takes into account by adding a reverse gear for practical manoeuvring activated electrically by the starter motor.
The K 1200 LT is further upgraded in the 2004 model year, now benefiting from an even more powerful engine with 116 hp and 120 Newton-metres (88 lb-ft) maximum torque, an electrohydraulically 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 makes its debut in 2002 as an enhanced variant of the K 1200 RS giving even greater emphasis to touring comfort. Boasting 130 hp maximum output, featuring a higher windshield and handlebar, optimized seating comfort and a case system fitted as standard, the K 1200 GT is even more of a genuine Gran Turismo, redefining the synthesis of sporting riding dynamics and supreme touring comfort in BMW's usual style and quality. The outstanding aerodynamic benefits offered by the full fairing ensure not only optimum protection from wind and weather, but also, in conjunction with a powerful engine, guarantee high average speeds on long distances.
The Second-Generation of Four-Cylinders
K 1200 S (2004-2008).
The K 1200 S makes 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 brand-new straight-four now fitted crosswise and displacing 1,157 cc, the K 1200 S has no predecessor and no role model in the history of BMW Motorrad, but is rather brand-new in every respect.
The technical highlights of this 167-hp Sports Machine are the very sloped angle of the cylinder bank tilted 55o 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 offers ESA (Electronic Suspension Adjustment) on the K 1200 S for the first time in series production, electronically controlled suspension operated at the touch of a button. 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 enters the segment of high-power Naked Bikes for the first time in 2004. Based on the K 1200 S, the new K 1200 R benefits from the straight-four engine with dry sump lubrication as well as innovative suspension technology with the BMW Duolever at the front and the BMW EVO Paralever at the rear.
Developing 163 hp 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 stand out particularly. Only a small windshield covers the front area above the headlight, but still offers efficient protection from the wind rushing by despite its small size.
Fitted with racing tyres, carbon trim and other motorsport components, the K 1200 R hits the headlines in the BMW Motorrad Power Cup held on the occasion of the MotoGP races in 2005.
K 1200 GT (2006-2008).
Following the success of its predecessor of the same name, the K 1200 GT opens 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 carry over the trendsetting suspension and engine technology of the K 1200 S into this new Sports Tourer, the innovative wheel guidance components - the Duolever and the EVO Paralever at the rear - making a signify cant contribution to the very dynamic riding qualities of the K 1200 GT.
The new machine is powered by BMW Motorrad's ultra-modern straight-four power unit fitted crosswise in the machine and developing 152 hp in the GT version, setting the benchmark in the Tourer segment at the time. Indeed,
no other manufacturer in the market emphasises dynamic performance more than BMW with the new K 1200 GT.
A comparison with the former model also reveals the most significant improvements offered by the new machine: the new K 1200 GT is more powerful (output + 17%), develops more torque (+ 11%), offers a longer theoretical range (+ 17%) and, at the same time, is lighter (- 6%), but is nevertheless able to carry a higher load (+ 19%).
K 1200 R Sport (2007-2008).
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.
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