The New BMW K 1200 S
The challenge begins
Sport is about being number one - on the BMW K 1200 S. Its main aim is: never trail the pack. It was created as a masterpiece of engineering for a thrilling riding experience, featuring a hitherto unknown combination of technology, performance and design. This innovative powerhouse on two wheels represents a challenge for every ambitious sports riders.
A slight turn of the throttle and the 123 kW (167 bhp) of the new 4-cyclinder engine catapults the BMW K 1200 S to the front of the pack. With a torque of 130 Nm it does the 0 - 100 km/h sprint in 2.8 seconds. The transverse installed power-plant offers everything a sports rider could wish for. The cylinder bank is tilted forward by 55°, the motorcycle’s center of gravity is very low due to the engine's extremely narrow width, and its leaning angle and ergonomics are excellent. The engine's power turns to precision in the newly designed 6-speed gearbox which works almost silently, with very short shift distances.
A new era has begun for ambitious sports riders. At the front the BMW K 1200 S features a world first in serial motorcycle production with the unique BMW Motorrad Duo-lever, as well as the newly designed and extremely light sports shaft drive, and BMW Motorrad EVO Para-lever at the rear. This sports suspension responds with extreme sensitivity and provides perfect feedback. The suspension of the BMW K 1200 S is also extremely adaptable to ensure safe road contact. An innovation which is unique in the motorcycling world is responsible for this: ESA (Electronic Suspension Adjustment - optional). The rider can adjust both the damping of the front and rear suspension while riding as well as the spring pre-load when stationary with the engine on. In this way the rider and machine can respond even more precisely to the road conditions.
Overall concept and model features
The new BMW K 1200 S sports machine with an engine power output of 123 kW (167 bhp) and a dry weight of 226.5kg (248 kg wet, including fuel) offers the highest standard of dynamic performance.
By introducing the BMW K 1200 S, Europe's largest and most successful manufacturer of motorcycles has enlarged its model range and entered the sporting high-performance motorcycle class, so far dominated by Japanese manufacturers. The BMW K 1200 S is a synthesis of high performance, precision, and safety.
Conceived as a sports machine from the start, the BMW K 1200 S is a singular and independent motorcycle within BMW's K family. It is radically new and innovative in every respect. The BMW K 1200 S has no predecessor in the current BMW Motorrad model range and follows no role model. On the contrary, the BMW K 1200 S is BMW's concept of a sports motorcycle - supreme riding precision and agility, high engine power output (specifically for road performance) and safe and superior handling in all practical situations.
The BMW K 1200 S does not compromise. Instead, it combines all the features previously regarded as largely incompatible. For example: sports performance and dynamism are combined with comfort, agility and ease of handling; supreme riding stability and high performance are coupled with everyday riding qualities; a slim-line sporting appearance is combined with efficient protection from wind and weather and superior rider ergonomics.
The BMW K 1200 S has all the virtues typical of BMW motorcycles but these have now ascended to a higher level. The new machine is fully suited to riding with a passenger and covering long distances; it offers a long service life and maintenance is minimal; it complies fully with environmental requirements (thanks to highly advanced emission management and a fully controlled three-way catalytic converter); and it offers active safety of the highest standard when braking (assured by the most advanced braking system on the market - BMW Motorrad Integral ABS).
The BMW K 1200 S is the only sports motorcycle to feature a maintenance-free shaft drive. In conjunction with the Para-lever swing arm (developed to an even higher standard and reduced in weight) the driveshaft has been optimised to a higher standard than before - its higher level of unsprung mass is virtually imperceptible even when the rider adopts a sports style of riding. Featuring innovative technology, and a new standard of riding characteristics in the sports bike segment, the BMW K 1200 S redefines the criteria for its class. The BMW K 1200 S will open up new customer potential for BMW Motorrad.
Unique concept for ideal riding dynamics and ergonomics
The first decision in the approximate five-year development period (from the initial idea through to production reality) was to carefully consider the overall concept regarding the drive-train, configuration and arrangement of the engine, and the overall package. It soon became clear that the advantages of a low centre of gravity, typical of all flat-twin and existing K-models, had to be retained on the new motorcycle. Research and fundamental examination of different engine concepts confirmed that (from the perspective of power, weight and space requirements) a four-cylinder power unit fitted crosswise was the optimum solution for high-performance motorcycles.
The only drawback with that configuration was a high centre of gravity. However, by tilting the cylinder bank forward to an extreme 55 degrees, and fitting the engine at it lowest possible point, BMW's engineers overcame that particular disadvantage. In addition, the entire engine block is extremely narrow to ensure adequate clearance when leaning into bends - allowing an exceptional angle of lean. Together with the extra-low, V-shaped radiator, the configuration interacts with the wheel suspension and guidance units to allow ideal frame curvature above the cylinder head to keep the motorcycle slim and narrow. With the frame profiles running close together at the rear, the new BMW K 1200 S shape also enables the rider's knees to be tightly pressed against the machine.
The overall result of this re-thought package is optimum geometric configuration of riding dynamics and ergonomics. The perfect seating position is tailored for the rider and allows an active riding posture with clear vision of the front wheel. It also has an appropriate standard of comfort and relaxation. The result is that the BMW K 1200 S handles dynamically and safely in every situation, making riding on the road confident and stress-free.
Innovations on the running gear and electronics
The BMW Duo-lever marks a quantum leap in technology in front-wheel suspension and makes a significant contribution to the motorcycle's excellent riding characteristics. By introducing this all-new, front-wheel suspension system BMW Motorrad has enhanced its leadership in suspension and running-gear technology and still ensures a sensitive response, at all times, with clear feedback from the front wheel. In conjunction with the four-cylinder concept, it also offers the advantage of compact dimensions.
BMW Motorrad is now introducing another world-first in motorcycle production with the ESA Electronic Suspension Adjustment which has advantages not previously seen. Based on CAN-bus technology, the advanced on-board network provides a wide range of different functions and reduces the procedures required for diagnostics by intelligently combining the motorcycle's electrical and electronic systems.
Highlights in technology at a glance
• supreme performance ensured by a free-revving, high-output straight-four power unit with features carried over from Formula 1
• cylinder bank of the four-cylinder, in-line engine tilted 55 degrees for an optimum centre of gravity
• engine output 123 kW (167 bhp), maximum torque 130 Nm (96 lb-ft) at 8,250 rpm
• Digital Motor Electronics and three-way catalytic emission management to the strictest environmental standards
• supreme riding precision and maximum riding stability provided by extra-rigid aluminium suspension with Duo-lever wheel guidance at the front and Evo Para-lever wheel guidance at the rear
• superior agility ensured by low, fully fuelled weight of 248 kg (547 lb) in road trim (DIN unladen weight including ABS)
• supreme handling thanks to ideal running gear geometry, optimum mass distribution, and a balanced all-round concept
• perfect balance ensured by a low centre of gravity
• ergonomically enhanced seating position for relaxed, active riding
• Electronically Adjustable Suspension (ESA) available as an option
• Integral ABS (part-integral system) available as a deletable option for superior active safety
• on-board network with electronic management; CAN-bus technology for enhanced functions combined with simple and straightforward wiring and low weight
• electronic immobiliser as standard
• maintenance-free, weight-optimised shaft drive
• enhanced aerodynamics with good protection from wind and weather
• wide range of features and accessories of the usual BMW standard dedicated to the K1200S.
Drive-train
Second generation of BMW four-cylinder motorcycle engines - radically new and with unique technical solutions
Fitted crosswise, the straight-four power unit of the BMW K 1200 S displaces 1157 cc. Maximum output is 123 kW (167 bhp) at 10 250 rpm; maximum torque of 130 Nm (96 lb-ft) is delivered at 8 250 rpm - with more than 70 per cent of the engine's maximum torque available from just 3 000 rpm. The engine power is easy to control at all times, which was BMW Motorrad's clear-cut objective when developing the new machine. Weighing just 81.3kg (179.3lb) including the clutch and gearbox, the engine is one of the lightest of its size in the market.
A well-conceived overall configuration, plus space-saving arrangement of auxiliary systems and the integrated gearbox enables a compact drive-train with ideal concentration of masses in the middle of the motorcycle. The crankshaft of the BMW K 1200 S is just 430 mm wide, placing the engine of the BMW K 1200 S closer to current 600cc power units than engines in the 1000cc-plus segment.
A wide range of exceptional and innovative details and solutions - with design concepts carried over from the BMW's motorsport technology - added up to the creation of a unique drive system. And, as in Formula 1, it is not individual features and qualities but the perfect interaction of technical solutions and the optimum integration of the chassis and suspension. In this respect, BMW's engineers overcame the inherent disadvantage of the relatively high centre of gravity of a conventional four-cylinder engine by applying a solution of typical BMW ingenuity: the engineers intelligently built on a well-known principle, enhancing its design concept to an even higher standard, by tilting the cylinder axis 55 degrees forward. This not only ensured a low centre of gravity but also provided the desired load on the front wheel - ideal for a sports riding - giving a precise feel of the surface and clear feedback from the front end. The more acute angle also provided space for an aerodynamically-efficient intake system (directly above the engine) to ensure an ideal flow of power.
This second generation of four-cylinder engines, in more than 80-years of BMW Motorrad, again lives up to BMW's principle of offering unique solutions superior to the usual standard. It is fair to say that in concept and design, the engine of the BMW K 1200 S must currently be the most advanced and engineered power unit of its kind in the world of motorcycling.
Crank drive and engine block - slim and slender despite its 1200cc capacity
The crankshaft of the BMW K 1200 S power unit is forged from one piece of heat-treated steel. It comes with eight counterweights and the usual crank angle of 180° for consistent firing intervals. The stroke / bore ratio ensures adequate overlap of the bearing journals for superior stiffness. The crankshaft runs in anti-friction bearings with the main and conrod bearing journals measuring 38mm in diameter.
The principle of supplying oil to the crankshaft and bearings has been adopted from Formula 1. Instead of feeding lubricant conventionally in a radial flow via the crankcase to each main bearing and from there via a ring groove to the bores on the conrod bearings, lubricant for the bearings is fed directly into the crankshaft in an axial flow. From there the lubricant flows through holes in the crankshaft and onto the conrod bearings. This makes the usual ring groove superfluous and keeps the bearing slimmer and more compact (even though it carries the same load on the same width otherwise occupied by the groove).
The advantage is adequate freedom of design for a very short and compact crankshaft and a minimum distance between cylinders to keep the overall engine slender and compact. Another advantage of this oil supply concept is that the oil entering the crankshaft no longer acts against centrifugal forces but is supported by those forces. This allows the oil pump to run at a much lower pressure - pump characteristics and the supply volume being optimised for minimum power loss. Finally, oil supply to the main cylinders follows the usual pattern via the main oil pipes in the crankcase, to where oil supply bores lead to the bearings.
Two of the crankshaft counterweights serve as gears for the primary clutch drive and for driving the two balance shafts. The other counterweights are perfectly designed for smooth-flow dynamics - the ratio between mass and inertia radius being optimised.
The camshafts in the cylinder head are driven by a chain running on a sprocket bolted to the right end of the crankshaft. Running in anti-friction bearings, the connecting rods are lightweight forged components made from heat-treated steel. Measuring 120mm in length, they interact with the short stroke of the engine to enhance running smoothness. Together with the anti-friction bearings, the connecting rods weigh a mere 413 grams.
Again, taking a typical BMW concept, the upper conrod opening has a bearing bush for a running life of more than 100,000 kilometres. The connecting rods are split horizontally by proven crack-technology breaking through the large conrod opening specifically on the middle level by means of a tensile force applied suddenly and instantaneously in a hydraulic process. The fracture surface provided in this way subsequently allows extremely accurate assembly without any further centring of components.
The engine has lightweight box-type pistons featuring an extra-short piston skirt and three rings (two compression and one oil removal ring). Despite the high compression ratio, the piston base and valve pockets are flat in configuration thanks to the flat surface of the combustion chamber. This enhances the thermodynamically-efficient combustion process and allows weight-optimised contours on the bottom of the piston. Piston weight, complete with the pins and rings, is only 299 grams. To dissipate heat on the piston base surface subject to high thermal loads, the surfaces are cooled by oil-injection nozzles in the crankcase and therefore extend service life.
To eliminate second-order free mass forces inevitable on a straight-four power unit, the crankcase, operating via a tooth belt, drives two balance shafts positioned below the crankshaft. This ensures 100 per cent balance and force compensation - the balance shafts running in roller bearings spaced symmetrically in front of, and behind, the crankshaft to avoid additional mass momentum. The balance shafts run at twice the speed of the crankshaft. To minimise dissipation of sound waves and noise, the balance weights are connected via elastomer elements to the balance shafts.
Horizontally divided cylinder crankcase in open-deck design
The two-piece crankcase is made of high-strength aluminium alloy with the two sections split down the middle of the crankshaft. Die-cast, the compact upper section forms an extremely stable structure made up of the four cylinders and the upper bearing frame for the crankshaft. The cylinder block, complete with water jacket, is an open-deck design. The cylinder liners are finished with a wear-proof, low-friction nickel-silicon dispersion coating. The lower section, made as a pressure-casting, forms the counterpart for the main crankshaft bearing and serves as a mounting point for the gearbox.
Cylinder head and valve-drive based on Formula 1 design and construction principles
The output, performance features, quality of combustion and fuel economy of an engine depend to a large extent on the cylinder head and valve drive. In its design and construction, the four-valve cylinder head of the BMW K1200S is conceived to ensure optimum duct geometry, compact dimensions, optimum thermodynamics, and a reliable thermal balance. The single design feature absolutely crucial to optimum design and configuration of the cylinder head is the valve angle. A particularly tight or narrow valve angle, for example, will provide a straight intake duct and compact combustion chambers for high compression and optimum efficiency. The criteria crucial to valve drive and optimum output at smooth and unproblematic engine speeds (not affecting the valve drive) are stiffness, the minimisation of moving masses, and maximum overlap on the valves.
In choosing the configuration of the BMW K 1200 S power unit, BMW's engine specialists have opted in favour of follower arm timing with two overhead camshafts. This offers the perfect combination of maximum stiffness and minimum weight on the moving valve drive components, together with compact design of the cylinder head. Indeed, it is no coincidence that this principle has become the usual standard on today's Formula 1 power units. BMW Motorrad's engine specialists were, therefore, able to capitalise on all BMW's experience in motorsport in terms of lubrication and surface coating.
The valve angle on the BMW K 1200 S power unit is 10 degrees on the intake and 11 degrees on the outlet side - figures so far not produced by any other contemporary engines. Out of the two overhead camshafts, only the outlet camshaft is driven by a chain from the crankshaft, the intake camshaft being driven by gear drive from the outlet shaft. The big advantage is that this requires only one sprocket on the cylinder head. The entire concept thus provides an even greater precision in valve timing and keeping the width of the cylinder head to a minimum.
The camshafts are located directly above the valves. The overall layout of the cylinder head allows an ideal 1:1 transmission ratio on the follower arms, thus keeping flexural tension to an absolute minimum and allowing the use of extremely delicate, lightweight levers. The speed limit chosen for practical purposes on production models is 11 000 rpm, while in mechanical terms the parts and components are able to take and withstand far higher speeds.
Valve diameter is 32mm on the intake and 27.5mm on the outlet side.
Record compression ratio
As already mentioned, the narrow valve angle keeps the combustion chambers compact with a flat upper surface. This is the prerequisite for a high level of geometric compression with a thermodynamically designed, largely flat piston floor. The compression ratio of 13:1 is unprecedented on a standard-production petrol engine, clearly confirming the ideal geometry of the combustion chambers with an ideal combustion process and optimum efficiency.
Oil supply identical to a race engine
The BMW K 1200 S comes with dry sump lubrication, otherwise found mainly on race engines. The advantages of this principle are supreme dependability with a steady oil flow, even under extreme conditions, and the flat design of the crankcase, keeps the entire engine in a flat and low position enabling a low centre of gravity. Not requiring an oil sump, the power unit is 60mm lower than with conventional construction. The oil reservoir is situated in the frame triangle behind the engine. The dual oil pump, driven by a chain from the clutch shaft, is housed in the rear crankcase area, drawing lubricant from the oil reservoir and feeding it under pressure initially to the oil filter (main flow filter) on the lower left side of the crankcase (within easy access from outside). From there, the pressurised oil flows into the main oil line in the crankcase and is spread out through internal holes leading to the lubrication points. The oil flowing back gathers at the lowest point in the crankcase in a recess within the bottom cap. The second pump delivers the oil flowing back, first to the oil cooler and then back to the oil tank through a patented re-flow system. The oil cooler is in the front fairing in a favourable flow position beneath the headlight. Finally, reflecting the overall philosophy of the machine, the oil cooler pipes are made of aluminium.
In an ingeniously simple process, the oil level is checked through a transparent, patented plastic tube outside the oil tank - used in service to drain oil from the tank with an overall volume of 4.2 litres or 0.92 Imp gals.
Engine cooling - keeping a cool head and good thermal balance
An intelligent cooling concept ensures a perfect thermal balance within the engine. The flow of coolant between the cylinder head and the cylinders is subdivided 73:27 by appropriately dimensioned flow cross-sections. The coolant flows crosswise through the cylinder head with re-cooled coolant entering the cylinder head on the "hot" outlet side.
This means that thorough cooling of the cylinder head ensures rapid dissipation of heat and an optimum temperature balance precisely where the thermal load is greatest.
The reduced flow of water on the cylinders enables the engine to warm up more quickly and reduces cold running wear and friction, also improving fuel economy.
The water pump is mounted on the left side of the cylinder head, where it is driven by the intake camshaft. This configuration and direct injection of cooling water into the cylinder head render the usual hoses superfluous and keeps the remaining hoses (leading to the radiator) extremely short. With the engine requiring only two litres of coolant, weight is once again reduced. The patented radiator also boasts motorsport technology: trapezoidal and appropriately curved in design, the radiator is fitted at the front lower end of the fairing - again for a lower centre of gravity. Thanks to the high degree of efficiency and aerodynamic optimisation of the fairing and flow conditions, a relatively small surface of only 920 sq cm ensures adequate dissipation of heat under all conditions. The integrated thermostat allows the engine to warm up quickly and the dirt trap fitted in front of the radiator has been optimised for perfect aerodynamics.
Alternator and starter
To keep the BMW K 1200 S slender and dynamic, the electrical ancillary units (as well as the drive systems) are fitted behind the crankshaft in the open space above the gearbox. The alternator is driven by the primary gear on the clutch and has a maximum output of 580 watts and maximum power of 42 amps. The layshaft starter is connected by a free wheel running on the alternator drive gear.
Power transmission - multiple-plate oil bath clutch and cassette-type gearbox
The BMW K 1200 S is also unique among production motorcycles in its gearbox technology: for the first time in the history of BMW shaft drive, the BMW K 1200 S features a multiple-plate oil-bath clutch (the diameter of the friction plates is 151mm), and a gearbox fully-integrated with the angle drive in the engine housing. The big advantages of this configuration, of course, are compact dimensions and efficient concentration of mass weight.
By introducing this concept, BMW Motorrad has not taken the usual approach. Instead, the gearbox is a separate, built-in unit commonly referred to as a cassette gearbox. This concept comes from motorsport where it allows rapid and efficient replacement of parts. On a production machine it offers advantages in the assembly process because the gearbox can be pre-assembled as a single unit. With the gears shifted by claws, the two-shaft gearbox is slender and light. The natural process of shifting from one ratio to another is conducted by a gearshift cylinder, gearshift forks, and slide wheels to provide positive engagement. To save weight the hollow gearshift cylinder is made of a high-strength aluminium alloy running in roller bearings. The shift forks are also made of aluminium and are lubricated by oil, supplied under pressure. A particularly smooth gearshift is ensured by anti-friction bearing bushes featuring a smooth bronze/teflon surface coating for minimum friction.
To keep the gearbox short and compact, the two transmission shafts run above one another. The gears themselves are straight-toothed, which not only improves transmission efficiency - albeit by only a minor factor - but also helps to keep the gearbox slender and avoid extra width. Thanks to the compact structure of the transmission and the minimisation of noise from the gearbox housing, running noise is reduced to a suitably low level.
Driveshaft to the rear wheel - indispensable and unique in sports machines
Like all large BMW motorcycles, the BMW K 1200 S features a driveshaft to convey power to the rear wheel. With the engine fitted crosswise, the shaft drive configuration requires two pivot points - the pivot unit leading from the gearbox is fitted in the gearbox cover.
The loss of efficiency resulting from such double-pivotal transmission is often overestimated because, in practice, it is only a few per cent. In comparison, studies confirm that because of a certain degree of wear and contamination, chain drive suffers a significant increase in friction. This reduces the degree of efficiency. Shaft drive operates without wear and maintains a consistent standard of efficiency throughout its full service life. The entire rear-wheel drive system is described in detail in the Suspension / Para-lever chapter.
New engine management - now featuring individual cylinder management with anti-knock control
The BMW K 1200 S boasts the most advanced digital engine management currently available on a motorcycle. Indeed, BMW's BMS-K (BMW Engine Management with Anti-Knock Control) Digital Motor Electronics is an in-house development specifically for motorcycles. The new generation of BMS-K technology was featured for the first time on the BMW R 1200 GS and has now been upgraded for four-cylinder power units. Its most significant advantages are fully sequential, cylinder-specific fuel injection, integrated anti-knock control, rapid processing of comprehensive sensor signals by means of the most advanced micro-electronics, compact layout, low weight, and self-diagnosis. By introducing this sophisticated management system, BMW Motorrad is further enhancing the unique qualities already held for so many years in electronic engine management.
Momentum-based engine management with alpha-n control
Momentum-based engine management evaluates a whole range of parameters and delivers torque and drive power specifically geared to running requirements while finely adjusting the engine running conditions.
The alpha-n management principle - with indirect determination of air volume intake as a function of the throttle butterfly angle and engine speed - has been exported from BMW's existing models and enhanced to a higher degree. Engine speed and the throttle butterfly angle are as before and (by means of a potentiometer) remain the basic factors for determining the engine operation. Then, by assessing additional engine and ambient parameters (including engine temperature, air temperature, ambient air pressure) the engine management system, focusing on control maps and built-in corrective functions, tailors the volume of fuel injected and the ignition timing point to specific, real-time requirements. Fuel injection is fully sequential so that fuel is injected individually into the intake ducts, precisely geared to the intake stroke in the respective cylinder.
Variable pressure control for optimum fuel supply
Variable fuel pressure control in the supply system is another first-time achievement on a production motorcycle. The system does not have a re-flow pipe or function, but delivers only the amount of fuel consumed by the engine. In practice, this highly efficient control of fuel supply allows fuel pressure to be varied almost at random for optimum fuel / air mixture formation. Fuel supply is thus tailored to actual requirements by the electrical fuel pump, applying a principle unique on a production machine (and protected by patents). The fuel / air mixture is masterminded by an oxygen sensor fitted at the junction point of the four exhaust manifolds for precise determination of exhaust emissions and their composition. The result is greater riding pleasure combined with even better environmental compatibility ensured by exemplary emission management and low fuel consumption, and enhanced by precise riding and a sensitive response.
BMS-K also comprises the automatic idle speed and cold-start control functions. Idle speed is increased automatically whenever required in the warming-up process. It is controlled by an idle speed stepper (bypass ducts for additional air) integrated into the airbox, and by specific adjustment of fuel injection volume. Measuring 46mm in diameter, the throttle butterflies come with patented operation featuring progressive adjustment. The butterfly position is predetermined by the rider turning the throttle and is controlled with greater precision by a step motor optimising engine response and fuel amount.
Incorporating various functions as one, the entire system is lighter than ever before. The three-piece injection rail, made of plastic, incorporates the fuel pressure sensor and rod-shaped high-energy ignition coils housed in the cylinder head enhance efficiency of the new engine management system.
High compression and anti-knock control for superior fuel economy
Fuel consumption of the BMW K 1200 S is 4.7 litres/100km at 90 km/h and 5.5 litres/100 km at 120 km/h. Considering the engine's power, performance and free-revving behaviour, this is truly outstanding in the supersports segment.
A major contributory factor to this superior efficiency is the unusually high geometric compression ratio of 13:1, a new record made possible only by anti-knock control. Following the BMW R 1200 GS, the BMW K 1200 S is the second BMW motorcycle to feature this protective function as standard. Two solid body sound sensors positioned between cylinders 1/2 and 3/4 detect any knock effects in the combustion process. The engine's electronic system responds by retarding the ignition and thus protecting the engine from possible damage. Conceived for unleaded premium-plus fuel (98 RON) under normal conditions, the engine, thanks to its efficient knock control, is able to run without the slightest problem and without manual intervention on premium (95 RON) or regular (91 RON) fuel. The only difference when using lower quality fuel is a slight decrease in maximum output and a slight increase in fuel consumption.
http://www.courantmotors.co.za/index.php/news/courant-bike
The challenge begins
Sport is about being number one - on the BMW K 1200 S. Its main aim is: never trail the pack. It was created as a masterpiece of engineering for a thrilling riding experience, featuring a hitherto unknown combination of technology, performance and design. This innovative powerhouse on two wheels represents a challenge for every ambitious sports riders.
A slight turn of the throttle and the 123 kW (167 bhp) of the new 4-cyclinder engine catapults the BMW K 1200 S to the front of the pack. With a torque of 130 Nm it does the 0 - 100 km/h sprint in 2.8 seconds. The transverse installed power-plant offers everything a sports rider could wish for. The cylinder bank is tilted forward by 55°, the motorcycle’s center of gravity is very low due to the engine's extremely narrow width, and its leaning angle and ergonomics are excellent. The engine's power turns to precision in the newly designed 6-speed gearbox which works almost silently, with very short shift distances.
A new era has begun for ambitious sports riders. At the front the BMW K 1200 S features a world first in serial motorcycle production with the unique BMW Motorrad Duo-lever, as well as the newly designed and extremely light sports shaft drive, and BMW Motorrad EVO Para-lever at the rear. This sports suspension responds with extreme sensitivity and provides perfect feedback. The suspension of the BMW K 1200 S is also extremely adaptable to ensure safe road contact. An innovation which is unique in the motorcycling world is responsible for this: ESA (Electronic Suspension Adjustment - optional). The rider can adjust both the damping of the front and rear suspension while riding as well as the spring pre-load when stationary with the engine on. In this way the rider and machine can respond even more precisely to the road conditions.
Overall concept and model features
The new BMW K 1200 S sports machine with an engine power output of 123 kW (167 bhp) and a dry weight of 226.5kg (248 kg wet, including fuel) offers the highest standard of dynamic performance.
By introducing the BMW K 1200 S, Europe's largest and most successful manufacturer of motorcycles has enlarged its model range and entered the sporting high-performance motorcycle class, so far dominated by Japanese manufacturers. The BMW K 1200 S is a synthesis of high performance, precision, and safety.
Conceived as a sports machine from the start, the BMW K 1200 S is a singular and independent motorcycle within BMW's K family. It is radically new and innovative in every respect. The BMW K 1200 S has no predecessor in the current BMW Motorrad model range and follows no role model. On the contrary, the BMW K 1200 S is BMW's concept of a sports motorcycle - supreme riding precision and agility, high engine power output (specifically for road performance) and safe and superior handling in all practical situations.
The BMW K 1200 S does not compromise. Instead, it combines all the features previously regarded as largely incompatible. For example: sports performance and dynamism are combined with comfort, agility and ease of handling; supreme riding stability and high performance are coupled with everyday riding qualities; a slim-line sporting appearance is combined with efficient protection from wind and weather and superior rider ergonomics.
The BMW K 1200 S has all the virtues typical of BMW motorcycles but these have now ascended to a higher level. The new machine is fully suited to riding with a passenger and covering long distances; it offers a long service life and maintenance is minimal; it complies fully with environmental requirements (thanks to highly advanced emission management and a fully controlled three-way catalytic converter); and it offers active safety of the highest standard when braking (assured by the most advanced braking system on the market - BMW Motorrad Integral ABS).
The BMW K 1200 S is the only sports motorcycle to feature a maintenance-free shaft drive. In conjunction with the Para-lever swing arm (developed to an even higher standard and reduced in weight) the driveshaft has been optimised to a higher standard than before - its higher level of unsprung mass is virtually imperceptible even when the rider adopts a sports style of riding. Featuring innovative technology, and a new standard of riding characteristics in the sports bike segment, the BMW K 1200 S redefines the criteria for its class. The BMW K 1200 S will open up new customer potential for BMW Motorrad.
Unique concept for ideal riding dynamics and ergonomics
The first decision in the approximate five-year development period (from the initial idea through to production reality) was to carefully consider the overall concept regarding the drive-train, configuration and arrangement of the engine, and the overall package. It soon became clear that the advantages of a low centre of gravity, typical of all flat-twin and existing K-models, had to be retained on the new motorcycle. Research and fundamental examination of different engine concepts confirmed that (from the perspective of power, weight and space requirements) a four-cylinder power unit fitted crosswise was the optimum solution for high-performance motorcycles.
The only drawback with that configuration was a high centre of gravity. However, by tilting the cylinder bank forward to an extreme 55 degrees, and fitting the engine at it lowest possible point, BMW's engineers overcame that particular disadvantage. In addition, the entire engine block is extremely narrow to ensure adequate clearance when leaning into bends - allowing an exceptional angle of lean. Together with the extra-low, V-shaped radiator, the configuration interacts with the wheel suspension and guidance units to allow ideal frame curvature above the cylinder head to keep the motorcycle slim and narrow. With the frame profiles running close together at the rear, the new BMW K 1200 S shape also enables the rider's knees to be tightly pressed against the machine.
The overall result of this re-thought package is optimum geometric configuration of riding dynamics and ergonomics. The perfect seating position is tailored for the rider and allows an active riding posture with clear vision of the front wheel. It also has an appropriate standard of comfort and relaxation. The result is that the BMW K 1200 S handles dynamically and safely in every situation, making riding on the road confident and stress-free.
Innovations on the running gear and electronics
The BMW Duo-lever marks a quantum leap in technology in front-wheel suspension and makes a significant contribution to the motorcycle's excellent riding characteristics. By introducing this all-new, front-wheel suspension system BMW Motorrad has enhanced its leadership in suspension and running-gear technology and still ensures a sensitive response, at all times, with clear feedback from the front wheel. In conjunction with the four-cylinder concept, it also offers the advantage of compact dimensions.
BMW Motorrad is now introducing another world-first in motorcycle production with the ESA Electronic Suspension Adjustment which has advantages not previously seen. Based on CAN-bus technology, the advanced on-board network provides a wide range of different functions and reduces the procedures required for diagnostics by intelligently combining the motorcycle's electrical and electronic systems.
Highlights in technology at a glance
• supreme performance ensured by a free-revving, high-output straight-four power unit with features carried over from Formula 1
• cylinder bank of the four-cylinder, in-line engine tilted 55 degrees for an optimum centre of gravity
• engine output 123 kW (167 bhp), maximum torque 130 Nm (96 lb-ft) at 8,250 rpm
• Digital Motor Electronics and three-way catalytic emission management to the strictest environmental standards
• supreme riding precision and maximum riding stability provided by extra-rigid aluminium suspension with Duo-lever wheel guidance at the front and Evo Para-lever wheel guidance at the rear
• superior agility ensured by low, fully fuelled weight of 248 kg (547 lb) in road trim (DIN unladen weight including ABS)
• supreme handling thanks to ideal running gear geometry, optimum mass distribution, and a balanced all-round concept
• perfect balance ensured by a low centre of gravity
• ergonomically enhanced seating position for relaxed, active riding
• Electronically Adjustable Suspension (ESA) available as an option
• Integral ABS (part-integral system) available as a deletable option for superior active safety
• on-board network with electronic management; CAN-bus technology for enhanced functions combined with simple and straightforward wiring and low weight
• electronic immobiliser as standard
• maintenance-free, weight-optimised shaft drive
• enhanced aerodynamics with good protection from wind and weather
• wide range of features and accessories of the usual BMW standard dedicated to the K1200S.
Drive-train
Second generation of BMW four-cylinder motorcycle engines - radically new and with unique technical solutions
Fitted crosswise, the straight-four power unit of the BMW K 1200 S displaces 1157 cc. Maximum output is 123 kW (167 bhp) at 10 250 rpm; maximum torque of 130 Nm (96 lb-ft) is delivered at 8 250 rpm - with more than 70 per cent of the engine's maximum torque available from just 3 000 rpm. The engine power is easy to control at all times, which was BMW Motorrad's clear-cut objective when developing the new machine. Weighing just 81.3kg (179.3lb) including the clutch and gearbox, the engine is one of the lightest of its size in the market.
A well-conceived overall configuration, plus space-saving arrangement of auxiliary systems and the integrated gearbox enables a compact drive-train with ideal concentration of masses in the middle of the motorcycle. The crankshaft of the BMW K 1200 S is just 430 mm wide, placing the engine of the BMW K 1200 S closer to current 600cc power units than engines in the 1000cc-plus segment.
A wide range of exceptional and innovative details and solutions - with design concepts carried over from the BMW's motorsport technology - added up to the creation of a unique drive system. And, as in Formula 1, it is not individual features and qualities but the perfect interaction of technical solutions and the optimum integration of the chassis and suspension. In this respect, BMW's engineers overcame the inherent disadvantage of the relatively high centre of gravity of a conventional four-cylinder engine by applying a solution of typical BMW ingenuity: the engineers intelligently built on a well-known principle, enhancing its design concept to an even higher standard, by tilting the cylinder axis 55 degrees forward. This not only ensured a low centre of gravity but also provided the desired load on the front wheel - ideal for a sports riding - giving a precise feel of the surface and clear feedback from the front end. The more acute angle also provided space for an aerodynamically-efficient intake system (directly above the engine) to ensure an ideal flow of power.
This second generation of four-cylinder engines, in more than 80-years of BMW Motorrad, again lives up to BMW's principle of offering unique solutions superior to the usual standard. It is fair to say that in concept and design, the engine of the BMW K 1200 S must currently be the most advanced and engineered power unit of its kind in the world of motorcycling.
Crank drive and engine block - slim and slender despite its 1200cc capacity
The crankshaft of the BMW K 1200 S power unit is forged from one piece of heat-treated steel. It comes with eight counterweights and the usual crank angle of 180° for consistent firing intervals. The stroke / bore ratio ensures adequate overlap of the bearing journals for superior stiffness. The crankshaft runs in anti-friction bearings with the main and conrod bearing journals measuring 38mm in diameter.
The principle of supplying oil to the crankshaft and bearings has been adopted from Formula 1. Instead of feeding lubricant conventionally in a radial flow via the crankcase to each main bearing and from there via a ring groove to the bores on the conrod bearings, lubricant for the bearings is fed directly into the crankshaft in an axial flow. From there the lubricant flows through holes in the crankshaft and onto the conrod bearings. This makes the usual ring groove superfluous and keeps the bearing slimmer and more compact (even though it carries the same load on the same width otherwise occupied by the groove).
The advantage is adequate freedom of design for a very short and compact crankshaft and a minimum distance between cylinders to keep the overall engine slender and compact. Another advantage of this oil supply concept is that the oil entering the crankshaft no longer acts against centrifugal forces but is supported by those forces. This allows the oil pump to run at a much lower pressure - pump characteristics and the supply volume being optimised for minimum power loss. Finally, oil supply to the main cylinders follows the usual pattern via the main oil pipes in the crankcase, to where oil supply bores lead to the bearings.
Two of the crankshaft counterweights serve as gears for the primary clutch drive and for driving the two balance shafts. The other counterweights are perfectly designed for smooth-flow dynamics - the ratio between mass and inertia radius being optimised.
The camshafts in the cylinder head are driven by a chain running on a sprocket bolted to the right end of the crankshaft. Running in anti-friction bearings, the connecting rods are lightweight forged components made from heat-treated steel. Measuring 120mm in length, they interact with the short stroke of the engine to enhance running smoothness. Together with the anti-friction bearings, the connecting rods weigh a mere 413 grams.
Again, taking a typical BMW concept, the upper conrod opening has a bearing bush for a running life of more than 100,000 kilometres. The connecting rods are split horizontally by proven crack-technology breaking through the large conrod opening specifically on the middle level by means of a tensile force applied suddenly and instantaneously in a hydraulic process. The fracture surface provided in this way subsequently allows extremely accurate assembly without any further centring of components.
The engine has lightweight box-type pistons featuring an extra-short piston skirt and three rings (two compression and one oil removal ring). Despite the high compression ratio, the piston base and valve pockets are flat in configuration thanks to the flat surface of the combustion chamber. This enhances the thermodynamically-efficient combustion process and allows weight-optimised contours on the bottom of the piston. Piston weight, complete with the pins and rings, is only 299 grams. To dissipate heat on the piston base surface subject to high thermal loads, the surfaces are cooled by oil-injection nozzles in the crankcase and therefore extend service life.
To eliminate second-order free mass forces inevitable on a straight-four power unit, the crankcase, operating via a tooth belt, drives two balance shafts positioned below the crankshaft. This ensures 100 per cent balance and force compensation - the balance shafts running in roller bearings spaced symmetrically in front of, and behind, the crankshaft to avoid additional mass momentum. The balance shafts run at twice the speed of the crankshaft. To minimise dissipation of sound waves and noise, the balance weights are connected via elastomer elements to the balance shafts.
Horizontally divided cylinder crankcase in open-deck design
The two-piece crankcase is made of high-strength aluminium alloy with the two sections split down the middle of the crankshaft. Die-cast, the compact upper section forms an extremely stable structure made up of the four cylinders and the upper bearing frame for the crankshaft. The cylinder block, complete with water jacket, is an open-deck design. The cylinder liners are finished with a wear-proof, low-friction nickel-silicon dispersion coating. The lower section, made as a pressure-casting, forms the counterpart for the main crankshaft bearing and serves as a mounting point for the gearbox.
Cylinder head and valve-drive based on Formula 1 design and construction principles
The output, performance features, quality of combustion and fuel economy of an engine depend to a large extent on the cylinder head and valve drive. In its design and construction, the four-valve cylinder head of the BMW K1200S is conceived to ensure optimum duct geometry, compact dimensions, optimum thermodynamics, and a reliable thermal balance. The single design feature absolutely crucial to optimum design and configuration of the cylinder head is the valve angle. A particularly tight or narrow valve angle, for example, will provide a straight intake duct and compact combustion chambers for high compression and optimum efficiency. The criteria crucial to valve drive and optimum output at smooth and unproblematic engine speeds (not affecting the valve drive) are stiffness, the minimisation of moving masses, and maximum overlap on the valves.
In choosing the configuration of the BMW K 1200 S power unit, BMW's engine specialists have opted in favour of follower arm timing with two overhead camshafts. This offers the perfect combination of maximum stiffness and minimum weight on the moving valve drive components, together with compact design of the cylinder head. Indeed, it is no coincidence that this principle has become the usual standard on today's Formula 1 power units. BMW Motorrad's engine specialists were, therefore, able to capitalise on all BMW's experience in motorsport in terms of lubrication and surface coating.
The valve angle on the BMW K 1200 S power unit is 10 degrees on the intake and 11 degrees on the outlet side - figures so far not produced by any other contemporary engines. Out of the two overhead camshafts, only the outlet camshaft is driven by a chain from the crankshaft, the intake camshaft being driven by gear drive from the outlet shaft. The big advantage is that this requires only one sprocket on the cylinder head. The entire concept thus provides an even greater precision in valve timing and keeping the width of the cylinder head to a minimum.
The camshafts are located directly above the valves. The overall layout of the cylinder head allows an ideal 1:1 transmission ratio on the follower arms, thus keeping flexural tension to an absolute minimum and allowing the use of extremely delicate, lightweight levers. The speed limit chosen for practical purposes on production models is 11 000 rpm, while in mechanical terms the parts and components are able to take and withstand far higher speeds.
Valve diameter is 32mm on the intake and 27.5mm on the outlet side.
Record compression ratio
As already mentioned, the narrow valve angle keeps the combustion chambers compact with a flat upper surface. This is the prerequisite for a high level of geometric compression with a thermodynamically designed, largely flat piston floor. The compression ratio of 13:1 is unprecedented on a standard-production petrol engine, clearly confirming the ideal geometry of the combustion chambers with an ideal combustion process and optimum efficiency.
Oil supply identical to a race engine
The BMW K 1200 S comes with dry sump lubrication, otherwise found mainly on race engines. The advantages of this principle are supreme dependability with a steady oil flow, even under extreme conditions, and the flat design of the crankcase, keeps the entire engine in a flat and low position enabling a low centre of gravity. Not requiring an oil sump, the power unit is 60mm lower than with conventional construction. The oil reservoir is situated in the frame triangle behind the engine. The dual oil pump, driven by a chain from the clutch shaft, is housed in the rear crankcase area, drawing lubricant from the oil reservoir and feeding it under pressure initially to the oil filter (main flow filter) on the lower left side of the crankcase (within easy access from outside). From there, the pressurised oil flows into the main oil line in the crankcase and is spread out through internal holes leading to the lubrication points. The oil flowing back gathers at the lowest point in the crankcase in a recess within the bottom cap. The second pump delivers the oil flowing back, first to the oil cooler and then back to the oil tank through a patented re-flow system. The oil cooler is in the front fairing in a favourable flow position beneath the headlight. Finally, reflecting the overall philosophy of the machine, the oil cooler pipes are made of aluminium.
In an ingeniously simple process, the oil level is checked through a transparent, patented plastic tube outside the oil tank - used in service to drain oil from the tank with an overall volume of 4.2 litres or 0.92 Imp gals.
Engine cooling - keeping a cool head and good thermal balance
An intelligent cooling concept ensures a perfect thermal balance within the engine. The flow of coolant between the cylinder head and the cylinders is subdivided 73:27 by appropriately dimensioned flow cross-sections. The coolant flows crosswise through the cylinder head with re-cooled coolant entering the cylinder head on the "hot" outlet side.
This means that thorough cooling of the cylinder head ensures rapid dissipation of heat and an optimum temperature balance precisely where the thermal load is greatest.
The reduced flow of water on the cylinders enables the engine to warm up more quickly and reduces cold running wear and friction, also improving fuel economy.
The water pump is mounted on the left side of the cylinder head, where it is driven by the intake camshaft. This configuration and direct injection of cooling water into the cylinder head render the usual hoses superfluous and keeps the remaining hoses (leading to the radiator) extremely short. With the engine requiring only two litres of coolant, weight is once again reduced. The patented radiator also boasts motorsport technology: trapezoidal and appropriately curved in design, the radiator is fitted at the front lower end of the fairing - again for a lower centre of gravity. Thanks to the high degree of efficiency and aerodynamic optimisation of the fairing and flow conditions, a relatively small surface of only 920 sq cm ensures adequate dissipation of heat under all conditions. The integrated thermostat allows the engine to warm up quickly and the dirt trap fitted in front of the radiator has been optimised for perfect aerodynamics.
Alternator and starter
To keep the BMW K 1200 S slender and dynamic, the electrical ancillary units (as well as the drive systems) are fitted behind the crankshaft in the open space above the gearbox. The alternator is driven by the primary gear on the clutch and has a maximum output of 580 watts and maximum power of 42 amps. The layshaft starter is connected by a free wheel running on the alternator drive gear.
Power transmission - multiple-plate oil bath clutch and cassette-type gearbox
The BMW K 1200 S is also unique among production motorcycles in its gearbox technology: for the first time in the history of BMW shaft drive, the BMW K 1200 S features a multiple-plate oil-bath clutch (the diameter of the friction plates is 151mm), and a gearbox fully-integrated with the angle drive in the engine housing. The big advantages of this configuration, of course, are compact dimensions and efficient concentration of mass weight.
By introducing this concept, BMW Motorrad has not taken the usual approach. Instead, the gearbox is a separate, built-in unit commonly referred to as a cassette gearbox. This concept comes from motorsport where it allows rapid and efficient replacement of parts. On a production machine it offers advantages in the assembly process because the gearbox can be pre-assembled as a single unit. With the gears shifted by claws, the two-shaft gearbox is slender and light. The natural process of shifting from one ratio to another is conducted by a gearshift cylinder, gearshift forks, and slide wheels to provide positive engagement. To save weight the hollow gearshift cylinder is made of a high-strength aluminium alloy running in roller bearings. The shift forks are also made of aluminium and are lubricated by oil, supplied under pressure. A particularly smooth gearshift is ensured by anti-friction bearing bushes featuring a smooth bronze/teflon surface coating for minimum friction.
To keep the gearbox short and compact, the two transmission shafts run above one another. The gears themselves are straight-toothed, which not only improves transmission efficiency - albeit by only a minor factor - but also helps to keep the gearbox slender and avoid extra width. Thanks to the compact structure of the transmission and the minimisation of noise from the gearbox housing, running noise is reduced to a suitably low level.
Driveshaft to the rear wheel - indispensable and unique in sports machines
Like all large BMW motorcycles, the BMW K 1200 S features a driveshaft to convey power to the rear wheel. With the engine fitted crosswise, the shaft drive configuration requires two pivot points - the pivot unit leading from the gearbox is fitted in the gearbox cover.
The loss of efficiency resulting from such double-pivotal transmission is often overestimated because, in practice, it is only a few per cent. In comparison, studies confirm that because of a certain degree of wear and contamination, chain drive suffers a significant increase in friction. This reduces the degree of efficiency. Shaft drive operates without wear and maintains a consistent standard of efficiency throughout its full service life. The entire rear-wheel drive system is described in detail in the Suspension / Para-lever chapter.
New engine management - now featuring individual cylinder management with anti-knock control
The BMW K 1200 S boasts the most advanced digital engine management currently available on a motorcycle. Indeed, BMW's BMS-K (BMW Engine Management with Anti-Knock Control) Digital Motor Electronics is an in-house development specifically for motorcycles. The new generation of BMS-K technology was featured for the first time on the BMW R 1200 GS and has now been upgraded for four-cylinder power units. Its most significant advantages are fully sequential, cylinder-specific fuel injection, integrated anti-knock control, rapid processing of comprehensive sensor signals by means of the most advanced micro-electronics, compact layout, low weight, and self-diagnosis. By introducing this sophisticated management system, BMW Motorrad is further enhancing the unique qualities already held for so many years in electronic engine management.
Momentum-based engine management with alpha-n control
Momentum-based engine management evaluates a whole range of parameters and delivers torque and drive power specifically geared to running requirements while finely adjusting the engine running conditions.
The alpha-n management principle - with indirect determination of air volume intake as a function of the throttle butterfly angle and engine speed - has been exported from BMW's existing models and enhanced to a higher degree. Engine speed and the throttle butterfly angle are as before and (by means of a potentiometer) remain the basic factors for determining the engine operation. Then, by assessing additional engine and ambient parameters (including engine temperature, air temperature, ambient air pressure) the engine management system, focusing on control maps and built-in corrective functions, tailors the volume of fuel injected and the ignition timing point to specific, real-time requirements. Fuel injection is fully sequential so that fuel is injected individually into the intake ducts, precisely geared to the intake stroke in the respective cylinder.
Variable pressure control for optimum fuel supply
Variable fuel pressure control in the supply system is another first-time achievement on a production motorcycle. The system does not have a re-flow pipe or function, but delivers only the amount of fuel consumed by the engine. In practice, this highly efficient control of fuel supply allows fuel pressure to be varied almost at random for optimum fuel / air mixture formation. Fuel supply is thus tailored to actual requirements by the electrical fuel pump, applying a principle unique on a production machine (and protected by patents). The fuel / air mixture is masterminded by an oxygen sensor fitted at the junction point of the four exhaust manifolds for precise determination of exhaust emissions and their composition. The result is greater riding pleasure combined with even better environmental compatibility ensured by exemplary emission management and low fuel consumption, and enhanced by precise riding and a sensitive response.
BMS-K also comprises the automatic idle speed and cold-start control functions. Idle speed is increased automatically whenever required in the warming-up process. It is controlled by an idle speed stepper (bypass ducts for additional air) integrated into the airbox, and by specific adjustment of fuel injection volume. Measuring 46mm in diameter, the throttle butterflies come with patented operation featuring progressive adjustment. The butterfly position is predetermined by the rider turning the throttle and is controlled with greater precision by a step motor optimising engine response and fuel amount.
Incorporating various functions as one, the entire system is lighter than ever before. The three-piece injection rail, made of plastic, incorporates the fuel pressure sensor and rod-shaped high-energy ignition coils housed in the cylinder head enhance efficiency of the new engine management system.
High compression and anti-knock control for superior fuel economy
Fuel consumption of the BMW K 1200 S is 4.7 litres/100km at 90 km/h and 5.5 litres/100 km at 120 km/h. Considering the engine's power, performance and free-revving behaviour, this is truly outstanding in the supersports segment.
A major contributory factor to this superior efficiency is the unusually high geometric compression ratio of 13:1, a new record made possible only by anti-knock control. Following the BMW R 1200 GS, the BMW K 1200 S is the second BMW motorcycle to feature this protective function as standard. Two solid body sound sensors positioned between cylinders 1/2 and 3/4 detect any knock effects in the combustion process. The engine's electronic system responds by retarding the ignition and thus protecting the engine from possible damage. Conceived for unleaded premium-plus fuel (98 RON) under normal conditions, the engine, thanks to its efficient knock control, is able to run without the slightest problem and without manual intervention on premium (95 RON) or regular (91 RON) fuel. The only difference when using lower quality fuel is a slight decrease in maximum output and a slight increase in fuel consumption.
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