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 a travel enduro – it also offers superb off-road driving capabilities. Whilst 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 balance power and weight, excellent ground clearance, long spring travel, precise wheel guidance and sophisticate ergonomics, giving excellent off-road driving and excellent long-distance performance.
2008 BMW F800GS
2008 BMW F800GS
2008 BMW F800GS
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 aluminium double-strut swing arm with a path-dependent cushioned spring strut and 215 mm spring travel and solid wire-spoke wheels. A 211" front wheel in the classic enduro dimensions of 90/90-21 gives running stability in slow off-road driving, whilst the rear wheel, with dimensions 150/70-17 ensures that the engine power is always transferred securely to the track.
The drive system 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 63 kW/85 HP at 7 500 min and, at 5 750 min sends a torque of 83 Newton metres 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 driving properties. When filled with petrol and ready to drive, the F 800 GS weighs in at just 207 kg.
Overview of the main features of the new GS model:
* F 800 GS as mid-class travel enduro with excellent off-road 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-gear transmission for excellent driving 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 aluminium.
* Spring strut with adjustable spring pretension and adjustable rebound damping, F 800 GS has WAD function (path-dependent damping
* as in the R 1200 GS).
* Long spring travel for comfort and off-road suitability.
* Excellent seat comfort for driver and pillion 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 off-road and touring use.
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 aluminium. 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 sequences 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 correcting 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 oscillating 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. Engine 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 too, 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 particular rev-proof. The valve play therefore only needs to be checked after 20,000 km at the earliest.
If required, the F 800 GS can also be fitted for use with normal petrol, which, however, reduces the peak performance by 1.5 kW/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 cooler 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 exchange 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 F800GS therefore has an O-ring chain with a division of 5/8 x 5/16.
A chain guide rail protects the aluminium 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. Whilst the six-gear 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 and modified.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 model, built in as a tubular space frame, offers a whole range of interesting details which improve the extraordinary off-road qualities of the GS model. 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 lay-out 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 advantages when the bike has to drive 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 realized, 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 drivers.
Made-to-measure telescopic forks.
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 particular large with this design, particular since the fixed tube diameter of 45 mm ensures excellent bending strength. Plastic deflectors combined with the front wheel covers provide protection against stones.
Aluminium double-strut swing arm at rear.
The rear wheel suspension of the GS models is similarly robust, with real slave qualities. It is based on an aluminium double-strut swing, die-cast in a single piece. The F 800 GS uses a directly hinged central spring strut with path-dependent damping and a spring travel of 215 mm The spring pre-tensioning can be adjusted on both spring strut elements 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 aluminium spoked wheels, size 21 x 2.15 at the front and 17 x 4.25 at the rear. The front wheel size of 21’’, 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. The wheels come with road-capable enduro tires as standard. For the F 800 GS, tires with a marked stud profile are also approved, and refitting is easy if the motorcycle is to be used mainly off-road.
The F 800 GS travels on tires measuring 90/90-21 at the front and 150/70-17 at the rear. Whilst the front wheel supports easy handling and minimizes braking torque, the rear wheel tire take account of the higher engine power.
Braking systems.
The front wheel has two fully floating brake discs 300 mm in diameter and double-piston sliding callipers. 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 callipers.
Modern two-channel ABS with improved rear wheel lift-off detection.
If required, the F800GS can be fitted ex-factory with a 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 driver only perceives a slight pulsing in the brake levers. In addition the BMW Motorrad ABS offers expanded diagnosis functions: the wheel rev sensors monitor their distance from the sensor wheel automatically and thus contribute to the vehicle’s outstanding safety. Riders who routinely drive off-road can deactivate the ABS system before off-road use.
On-board electrics with CAN bus and immobilizer.
The electrical systems in the new GS are also at the top of the range, and work 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 cable required, allows all control devices to be networked and thus simplifies the preparation of comprehensive diagnoses. In addition, there is no need for conventional fuse cut-outs, 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 bit 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 generator ensure a reliable power supply.
The cockpit with its analogue instruments arranged above each other and its information display including on-board clock provides the driver 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 the characteristic face of the youngest BMW generation.
The reflectors, familiar from the BMW R 1200 GS and loved by night-time drivers 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 full beam, the dipped 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 off-road use.
Although the long spring travel in an enduro generally result in higher seats, drivers of the new GS will easily be able to touch the ground with their feet.
The strongly waisted seat is offered in two heights, with seat heights of 880 or 850 mm available for the F 800 GS.
For relaxed driving the new GS has a vibration-absorbent handlebar – made from conically shaped aluminium tubing, and folding, wide steel footrests with hollow-chamber rubber surfaces. To be able to stand securely in the footrests off-road, 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 a travel motorcycle, the GS also provide excellent comfort for the passenger. The seat length and footrest position allow the passenger to relax, whilst 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 windscreen with their M-shaped design have been optimized in a wind tunnel.
The 16-litre 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 tank rucksack – which does not entirely deserve its name here – can be left in place as the tank is filled. Because the lockable filler nozzle is easily accessible on the right-hand side of the vehicle level with the pillion seat.
The color variants chosen underline the character of the new off-road bike. For the market launch, the F 800 GS will be appearing in plain Sunset Yellow/Black or Dark Magnesium Metallic Matt.
Source and Photos : Motorbike.Org
