2008 BMW F 800 GS Preview

Characteristics and technology.

2008 BMW F 800 GS

For BMW Motorrad, the abbreviation “GS” is not an empty promise. This will be demonstrated in the future by the F 800 GS too, in continuation of a long tradition. The new model not only offers the typical qualities of an adventure-tourer – it also offers superb offroad riding capabilities. While large-capacity enduros sometimes reach their limits because of their weight and overall design, the new F 800 GS is completely unstoppable. The overall package combines balanced power and weight, excellent ground clearance, long spring travel, precise wheel guidance and sophisticated ergonomics, giving excellent offroad riding and excellent long-distance performance.

The chassis combines all the ingredients that a real enduro needs: a sturdy steel tube frame that allows a steering lock of 42 degrees, a rigid upside-down fork with 230 mm spring travel, a sturdy aluminum double-strut swing arm with a path-dependent cushioned spring strut and 215 mm springtravel and solid wire-spoke wheels. A 21-inch front wheel in the classic enduro dimensions of 90/90-21 gives running stability in slow offroad riding, while the rear wheel, with dimensions 150/70-17 ensures that the engine power is always transferred securely to the track.

The engine is the parallel twin from the F 800 S modified for the new usage, with its cylinders now only inclined 8.3 degrees forward. The strong, liquid-cooled four-valve two-cylinder is particularly convincing because of its spontaneous response, its impressive torque and its low fuel consumption. Nominally, the engine provides 85 HP at 7 500 min–1 and, at 5 750 min–1 sends a torque of 61 pound-feet to the sliding bearing based crankshaft. Thanks to the regulated three-way catalytic converter and secondary air system, the twin releases its power in a way that is absolutely environmentally friendly. The mass balance is provided by a system that is unique in standard motorcycle design: an additional swivel con-rod balances the first and second level mass forces and ensures that the two-cylinder functions with the minimum of vibrations.

The low dry weight of 178 kg makes a major contribution to the dynamic riding properties. When filled with fuel and ready to ride, the F 800 GS weighs in at just 207 kg.
 
The F 800 GS offers an excellent level of seat comfort for both rider and passenger, along with a high standard of safety features. If required, it can be fitted ex factory with two-channel ABS that can be switched off. In addition, the extensive range of BMW accessories meets the further individual wishes of our demanding customers, as always.

Overview of the main features of the new F 800 GS:

• F 800 GS as mid-class adventure-tourer with excellent offroad properties and long-distance capabilities.
• Liquid-cooled parallel twin with 798 cc capacity, four-valve technology and unique mass balance.
• Rev-proof DOHC valve drive via cam followers.
• Manifold injection with electronic engine management BMS-KP, lambda probe and regulated three-way catalytic converter plus secondary air system.
• Closely stepped six-speed transmission for excellent riding performance.
• Dirt-resistant secondary drive via O-ring chain.
• Torsion-resistant tubular steel frame with unusual gusset plate reinforcement of steering head.
• Easy handling and extremely tight turning circle.
• Stable telescopic fork, USD fork with upright tube diameter 45 mm.
• Double-strut swing arm in die-cast aluminum.
• Spring strut with adjustable spring pre-tension and adjustable rebound damping; WAD function (path-dependent damping as in the R 1200 GS).
• Long spring travel for comfort and offroad suitability.
• Excellent seat comfort for rider and passenger.
• Tank underneath seat, for best center of gravity, with easily accessible fill opening.
• Powerful braking system, with ABS if required.
• Air filter and battery positioned behind steering head for easy maintenance.
• Wide range of accessories for offroad and touring use.

2008 BMW F 800 GS

The most important details at a glance: BMW F 800 GS

• 85 HP   
• Valve timing like F 800 S  
• Wide radiator  
• Offroad-look fairing  
• High windscreen  
• USD telescopic fork  
• WAD spring strut  
• Spoked wheels  
• 21-in front wheel  
• Double-disc brake, floating, front  
• Aluminum handlebar  
• 880/850 mm seat height  
• Ready-to-ride weight 207 kg  

Modified two-cylinder.

The parallel twin familiar from the F 800 S/ST models forms the basis for the GS drive. For the new usage, however, some aspects of the engine have been modified. In order to allow long spring travels with a wheel spacing that remains moderate, plus an ideal distribution of weight, the cylinders are now only angled forward by 8.3 degrees instead of the 30 degrees with the F 800 S/ST. This solution has been made possible by a new design for the lower engine housing section made from die-cast aluminum. It contains application points for the engine protection plate and provides the ideal working conditions for the semi-dry sump lubrication. In addition, the cylinder head has been reinforced in the area of the frame connection at the front on the right. The GS engine has a modified clutch cover which creates more space in the footrest area and more room for a new oil dipstick and a changed clutch release shaft. Finally, the water pump housing and cooling hose connections have been adapted to the new position of the engine. The side-effect of these modifications is that the engine is a kilogram lighter than the unit used in the S/ST model series.

Like the famous F 800 engine, the transverse parallel twin works with an even firing order (360° ignition offset) without crank offset on the crankshaft. Because there is one firing cycle for each crankshaft rotation, the sound is deliberately like that of boxer engines which work with an identical firing offset. Most importantly, however, the even firing sequence creates the best conditions for a balance load change with high torque yield.

Unique mass balance.

The mass forces are offset by a balancing mechanism that is unique in series engine design. Instead of having conventional counterweight shafts, the oscillating mass forces are balanced by a joint system on the center of the crankshaft with deliberately positioned counterweight masses: an eccentric on the crankshaft offset against the crank pins by 180° carries what is known as a balancing connecting rod. This connecting rod is hinged to an approximately horizontal balancing rocker. The kinematics are designed in such a way that the balancing connecting rod moves contrary to the two engine connecting rods. Because of being guided through the relatively long rocker, an almost linear swivel movement of the connecting rod head is achieved – to put it precisely, the small connecting rod eye describes a slightly curving path. The mass distribution at the connecting road head and rocker is chosen in such a way that the mass forces resulting from the swinging movement combat, in every crankshaft position, the oscilating mass forces from the crank drive (piston and con-rod proportion). This means that first and second order mass forces are almost completely eliminated, resulting in low-vibration engine running.

Lubrication system.

The oil circulation system also includes a number of sophisticated details. In order to prevent punch losses, a semi-dry sump lubrication system has been designed which works without any separate engine oil tank. Lubricant coming from the main bearings collects in a tray which also holds the balancing system and which is sealed off from the actual oil tray. Oil in this area is constantly vacuumed up by an oil pump and transported to the transmission housing, before running from there, under no pressure, via openings in the crank housing into the oil tray. The oil pressure pump supplies the lubricating oil system from this reservoir.

Camshafts matched to enduro requirements.

The cylinders in the GS engine are fitted with a high-tech cylinder head. As in the new engines in the K model range, here also, two upper camshafts driven by a toothed chain rotate and control four valves per cylinder via cam followers. The F 800 GS, unlike the S/ST models, uses slightly modified camshafts which help the engine develop its power in a way that is ideal for enduros: with excellent torque, even and easily controllable. The valve drive via cam followers is low-wear, only produces minimal friction losses and is particularly rev-proof. The valve play therefore only needs to be checked after 20,000 km at the earliest.

Mixture preparation.

Other features that are typical of BMW include the mixture preparation, which is via a manifold injection with BMS-KP engine control and two 46 mm throttle valves. The injection quantity is determined by the specially tuned engine control, not only via the injection period but also via the pressure that the fuel pump provides, depending on the power requirement. The fuel system operates without return and only carries the quantity that the engine actually needs. Because of this economical, patented regulation system, the fuel pressure can be modified within a wide range so that the mixture is always ideal. To measure the fuel quantity supplied, not only the well-known parameters such as load, engine speed and temperature are used, but also the residual oxygen content in the exhaust gas. The corresponding information is provided by a lambda probe positioned at the point where the manifolds join. This is followed immediately by the three-way catalytic converter, provided as standard, which quickly warms up after the cold start and can thus start its conversion work quickly.

The air necessary to form the mixture reaches the new suction silencers via suction snorkels positioned in the cool air stream. The positioning well above the engine, which is good for both on-road and off-road riding, and the large volume, which supports torque were made possible by the positioning of the tank under the seat. The suction snorkels of the F 800 GS are visible as a design element.

Exhaust system.

The completely new, weight-optimized exhaust gas system is made completely from high-grade steel and weighs in at just 8.5 kg. The single-wall manifold system is connected with the silencer via a plug connection with tension spring. The attachment of a slip-on silencer is therefore easy and less costly, especially since the catalytic converter is integrated into the manifold. The end silencer provided as standard is constructed as a two-chamber silencer in a combined absorption/reflection design, offers a gas flow volume of 8 litres and is mounted on the left side of the motorcycle, half way up. The F 800 GS is fitted with a secondary air system which, in combination with the regulated catalytic converter, reduces the emission of pollutants to EU3 requirements.

High-revving with great torque.

2008 BMW F 800 GS

It is not only the modern injection system that ensures a prompt response from the F 800 GS twin; its low centrifugal mass also contributes to its agile power development. Even at the bottom of its rev range, the four-valver, which, with a bore-stroke ratio of 82 to 75.6 mm, is not particularly short-stroked, soon speeds up and releases a good 90% of the maximum torque in the broad range between 4 000 and 7500 min–1. Between 5 000 and 8 000 min–1, the engine develops its power dynamically, accompanied by a unique sound. The nominal performance data of the 798 cc twin – 85 HP at 7 500 min–1 and 61 lb-ft at 5 750 min–1 – therefore give an incomplete picture of the potential that is available in practice.

In combination with the low total weight and closely stepped six-speed transmission, the F 800 GS accelerates from 0–100 km/h in about 4 seconds, and the top speed is over 200 km/h.

But it is not only the acceleration of the new GS model that is impressive; its traction is also remarkable. The BMW development engineers have focussed quite deliberately on the smooth, confident development of power in the mid engine speed range rather than on absolute peak performance. Sporting riders will be bowled over by the engine’s acceleration, while tourers will enjoy the twin’s strong traction with minimal shifting.

The parallel twin, which has been optimized for enduro operation, not only manages to walk the tightrope between powerful torque and dynamic acceleration, it also proves that good performance does not necessarily involve high fuel consumption. Ridden over country roads, a consumption of well below 5 liters of super octane fuel per 100 km is perfectly possible. If required, the F 800 GS can also be fitted for use with normal octane fuel, which, however, reduces the peak performance by 2 HP and increases fuel consumption slightly. This modification is carried out by calling up a characteristic map in the control software, and can be cancelled again at any time.

The sophisticated engine concept shows additional technical finesse in its peripherals. The water pump, for example, is on the right of the cylinder head and is driven by a cog wheel unit on the camshaft. The advantageous positioning of the pump – directly behind the radiator with integrated thermostat – means that only short hose connections are needed. The engine therefore looks particularly compact and tidy. An oil-water heat exchanger next to the easily accessible oil filter ensures that the engine warms up particularly quickly after a cold start. In addition, the heat exchanger also limits the engine oil temperatures.

Rear wheel drive via robust O-ring chain.

Because motorcycles suitable for off-road use are often used on roads that are unfinished, they need a secondary drive that is not sensitive to dirt. The F 800 GS therefore has an O-ring chain with a division of 5/8 x 5/16.

A chain guide rail protects the aluminum rocker from damage. Four asymmetrical drive dampers provide shock absorption for the chain wheel bearer which is taken exactly over the full-floating axle via a grooved ball bearing.

While the six-speed transmission is taken from the F 800 S/ST models and only the transmission output shaft has had to be modified to the chain drive, the end transmission ratio has been changed. The F 800 GS thus works with a transmission ratio of 1:2.625 (16/42 Z).

A sturdy tubular steel frame.

The tubular steel frame designed specially for the new GS models, built as a tubular space frame, offers a whole range of interesting details which improve the extraordinary off-road qualities of the GS models. The slim steering head, for example, which is integrated with total stability into the frame structure, allows a steering lock stop of 42 degrees. The steering head is fixed using a completely new layout of gusset plates which have considerably reduced the design width without affecting the stability of the frame. The steering lock is also improved by the fact that the steering lock is positioned in front of the handlebar. Off-road, the small turning circle of the GS is particularly advantageous when the bike has to be ridden through trial sections at walking speed.

The tubular space frame in manganese-alloy steel integrates the engine as a bearing element into the framework. The frame tubes are brought together in the area of the rocker bearings in forged steel parts. The frame tail made from rectangular steel pipe is taken up by the main frame via four screw connections and carries the new fuel tank (capacity 16 litres) which is positioned under the seat. The new design was not only required because of the modified engine. In the front part of the bench seat, not only are the main frame and frame end very narrow – the seat itself and the covering of the suction silencer are very streamlined. This means that, in relation to the seat height, an incredibly short arc has been achieved, which is the decisive dimension for being able to touch the ground. The result is that the GS provides perfect seating both for giants of the road and for smaller riders.

Made-to-measure telescopic forks for both models.

Because of the very long spring travel of 230 mm, an upside-down telescopic fork is the best choice for the F 800 GS. The overlapping of the fixed and sliding tubes is particularly large with this design, especially since the fixed tube diameter of 45 mm ensures excellent bending strength. Plastic deflectors combined with the front wheel covers provide protection against stones.

Aluminum double-strut swing arm at rear.

The rear wheel suspension of the GS is similarly robust, with real slave qualities. It is based on an aluminum double-strut swingarm, die-cast in a single piece. The F 800 GS uses a directly hinged central spring strut with path-dependent damping and spring travel of 215 mm. The spring pre-tensioning can be adjusted using a handwheel, so that the rear wheel suspension can easily be adjusted for one- and two-person use. The tension stroke of the suspension can also easily be adjusted to individual requirements.

Wheels and tires for the required purpose.

The F 800 GS travels on aluminum spoked wheels, size 21 x 2.15 at the front and 17 x 4.25 at the rear. The front wheel size of 21-in, which is normal in enduro sports, gives greater riding stability because of the greater gyroscopic forces, which can be an inestimable advantage on loose ground. Road-capable enduro tires are standard, but tires with a marked stud profile are also approved, and refitting is easy if the motorcycle is to be used mainly offroad.

The tire sizes are also proof that the F 800 GS is tailored to its preferred area of use. It travels on tires measuring 90/90-21 at the front and 150/70-17 at the rear. While the front tire supports easy handling and minimizes braking torque, the rear tires takes account of the high engine power.

Braking systems matched to on- and off-road requirements.

The braking system is also matched to the intended purpose. Because the F 800 GS is capable of reaching high speeds, the front wheel has two fully floating brake discs 300 mm in diameter with double-piston sliding calipers. At the front the steel-reinforced brake lines are laid in such a way that they do not push through the cockpit fairing when the telescopic fork is compressed. At the rear wheel, the GS is slowed down by a 265 mm disc brake with single-piston sliding caliper.

Modern two-channel ABS with improved rear wheel lift-off detection.

If required, the F 800 GS can be fitted ex-factory with two-channel ABS. The current generation of BMW Motorrad ABS is characterized not only by its compact design and low weight, but also by its very short braking paths. The pressure modulator controls the optimum braking pressure in the regulating range via intake valves that are adjusted on a linear basis and is characterized by its very fast, fine regulating intervals. The valves with infinitely variable cross-section openings also ensure that the rider only perceives a slight pulsing in the brake levers. In addition the BMW Motorrad ABS offers expanded diagnosis functions: the wheel speed sensors monitor their distance from the sensor wheel automatically and thus contribute to the motorcycle’s outstanding safety. Riders who routinely ride off-road can deactivate the ABS system before off-road use.

On-board electrics with CAN bus and immobilizer.

2008 BMW F 800 GS

The electrical system in the new GS is also at the top of the range, and works with an innovative CAN bus system. As in the sister models in the F 800 model series, the single-wire system (SWS) has many advantages: it reduces the amount of wiring required, allows all control devices to be networked and thus simplifies the preparation of comprehensive diagnoses. In addition, there is no need for conventional fuses, since the system automatically switches off the component in question in the event of a malfunction.

Since the introduction of CAN bus technology, an electronic immobilizer has been part of the standard equipment on BMW motorcycles. More than the right key is needed to start the engine – in addition, the chip integrated into the BMW key must report the right code to the ring antenna of the combined steering and ignition lock. Only then does the engine control allow the vehicle to be started. This technology offers the safest, most reliable protection against vehicle theft available today.

The electrical plug connections are waterproof and thus unsusceptible to faults. A 14 ampere-hour battery and a 400 W alternator ensure a reliable power supply.

The cockpit with its analog instruments arranged above each other and its information display including on-board clock provides the rider with information at a glance. As an item of special equipment, BMW offers an on-board computer with further functions such as gear display and stopwatch.

The asymmetrical double headlight with glass-clear plastic cover give
the GS models the characteristic face of the youngest BMW generation. The reflectors, familiar from the BMW R 1200 GS and loved by night-time riders because of their superb use of light, are enclosed in a new plastic housing and are fitted with two H7 headlight bulbs. On switching to high beam, the low beam remains active. The headlights are fixed using an unbreakable, lightweight plastic support which also takes the cockpit and the sturdy plastic cladding made from high-strength polypropylene.

Optimum seat design for touring and offroad use.

Although the long spring travel in an enduro generally results in a higher seat, riders of the new GS models will easily be able to touch the ground with their feet. The strongly waisted seat is offered in two heights — 880 or 850 mm. The low arc length is also due to the frame, which is very streamlined in the critical area. The seat is locked at the front in a vibration-absorbing holder. This layout means that there is an uninterrupted transition between the fairing, the frame and the seat.

For relaxed riding the new F 800 GS has a vibration-absorbent handle-bar made from conically shaped aluminum tubing, and folding, wide steel footrests with hollow-chamber rubber surfaces. To be able to stand securely in the footrests offroad, the rubber surfaces can also be removed.

The wide, upswept handlebars are fitted with easy-to-reach fittings; the grip width of the levers can be adjusted. The combined ignition/steering lock is also conveniently positioned in front of the handlebars.

As one might expect from an adventure-tourer, the GS also provides excellent comfort for the passenger. The seat length and footrest position allow the passenger to relax, while the long side holder brackets at the rear provide a secure grip. Last but not least, the fairing discs offer moderate wind protection, thus helping the passenger to travel in comfort. The high windscreen with its M-shaped design has been optimized in a wind tunnel.

The 16-liter fuel tank under the seat has proved a great advantage on long trips, not only because long distances can be travelled, thanks to the motorcycle’s low fuel consumption, but also because the tankbag can be left in place as the tank is filled. The lockable filler nozzle is easily accessible on the right-hand side of the motorcycle level with the passenger seat.

The color variants chosen underline the character of the new offroad bike. For the market launch, the F 800 GS will be appearing in Sunset Yellow/Black or Dark Magnesium Metallic Matt.
 

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