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With two completely new enduro models, the F 800 GS and F 650 GS, BMW Motorrad is not just expanding its range of products but also presenting a worthy successor to the successful single-cylinder F 650 GS.
Even when parked, the amazing off-road-capable parallel twin F 800 GS travel enduro, with its sturdy appearance and long spring travel, implies what it can do off-road. It hints at fun riding on all types of road with added stamina and durability on journeys where the destination can only be reached on gravel tracks.
The F 800 GS’s smaller brother, the F 650 GS, which also has a parallel twin-cylinder engine, is aimed at people who do not need quite as much spring travel and are looking for a little less adventure. With its low seat height, it is an outstanding all-rounder; easy to control, provides plenty of power combined with economy, and is ideal for everyday use.
High levels of stability allied to easy handling are features shared by the two new GS models. Both offer high-quality workmanship, a safe chassis and impressive modern engines for maximum riding pleasure.
The parallel twins’ drive comes from the well-established F 800 model series, but beyond this, the new enduro models have been completely redesigned. A new frame and new wheel suspension with new spring-shock absorber elements are strong features.
They will surpass the expectations of even the most demanding enduro riders. The previous model’s belt drive and single-strut swing arm, which are ideal for pure on-road use, have been replaced by a light chain drive in combination with a very stable and attractive aluminium profile, double-strut swing arm. These are more advantageous when off-road riding. The new GS models are not only in their element on twisty roads – it will also perform exceptionally off-road too.
The F 800 GS combines road and touring capabilities with superior off-road characteristics. It thus performs on both terrains in a way that has never before been achieved in its class. BMW Motorrad has positioned the versatile travel enduro at an attractive price, thus adding a real asset to the market.
The new F 650 GS differs from its higher capacity variant by featuring a lower seat height, lower weight and slightly reduced engine power. It is ideal for newcomers to the genre or as a sturdy all-round motorcycle for all purposes. Compared with its single-cylinder predecessor, the new F 650 GS is an improvement in every area. Despite its designation, which usually refers to the engine size, the F 650 GS has the same 800cc twin-cylinder engine as the F 800 GS. With slightly reduced engine power (71 instead of 85HP) the focus for the F 650 GS is on high torque at lower engine speeds coupled with excellent economy. Despite this it delivers over 20HP more power than its predecessor. The 800cc (sic) F 650 GS guarantees riding pleasure no matter where it goes.
2. Vehicle characteristics and technology
For BMW Motorrad, the GS designation is not an empty promise.
This is brilliantly demonstrated by the F 800 GS and continues a long tradition. The new model not only offers the typical qualities of a travel enduro – it also offers superb off-road riding capabilities. While large-capacity enduros sometimes reach their limits because of weight and its associated design, the new F 800 GS is completely uncompromising. The overall package combines balance, power and weight, excellent ground clearance, long spring travel, precise wheel guidance and sophisticated ergonomics. The result is excellent off-road riding and superb long-distance performance.
The chassis combines all the features of a true enduro: a sturdy steel-tube frame that allows a steering lock of 42 degrees; a rigid upside-down forks with 230mm spring travel; a sturdy aluminium double-strut swing arm with a path-dependent cushioned spring strut and 215mm spring
travel; and solid wire-spoke wheels. A 21.1-inch front wheel in the classic enduro dimensions of 90/90-21 gives running stability during slow off-road riding. The rear wheel, with dimensions 150/70-17 ensures that the engine power is always efficiently transferred to the surface.The drive system is the F 800 S parallel twin – now with its cylinders inclined only 8.3 degrees forward – modified for the new demands. The strong, liquid-cooled four-valve twin-cylinder engine is particularly suitable because of its instantaneous response, impressive torque and low fuel consumption. Nominally, the engine provides 63kW / 85HP at 7,500 min–1 and, at 5 750 min–1 outputs a torque value 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 power that is environmentally friendly. The mass balance is provided by a system that is unique in standard motorcycle design: an additional swivel conrod balances the first and second level mass forces and ensures that the twin-cylinder engine produces minimum vibration.The low dry weight of 178kg makes a major contribution to the dynamic riding properties. When filled with petrol the F 800 GS weighs only 207kg.
The F 650 GS is 8kg lighter and with a much lower seat height is the ideal motorcycle for newcomers. Technically, it is based on its larger variant but the cast metal wheels and lower ground clearance indicate that it prefers on-road use. Other distinguishing features are the smooth-surfaced side fairings, the low windscreen, other spring elements, and slightly lower engine power. With 52kW / 71HP at 7, 000 min–1 and a maximum torque of 75Nm even at 4,500 min–1, there’s still plenty of power. Because of the reduced power, there is no need for a secondary air system because fewer un-combusted gases enter the exhaust system. A 25kW / 34HP version is also available for riders who have only just passed their test.
The two F models offer an excellent level of seat comfort for the driver and pillion passenger. If an even higher standard of safety is required the enduros can be fitted at the factory with a two-channel ABS that can be switched off. In addition, the extensive range of BMW accessories meets the individual demands of BMW’s customers.
Overview of the main features of the new GS models
• F 800 GS as a mid-class travel enduro with excellent off-road properties and long-distance capabilities.
• F 650 GS as an all-round variant ideal for newcomers, designed to be slightly stronger for on-road use and easier to control.
• Liquid-cooled parallel twin with 798cc 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 (only for F 800 GS).
• 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 and rein¬forced steering head.
• Easy handling and extremely tight turning circle.
• Spring strut with adjustable spring pre-tension 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 on the F 800 GS.
• Excellent seat comfort for rider and pillion passenger.
• Tank underneath seat for best centre 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.
Modified twin-cylinder engine
The parallel twin familiar from the F 800 S/ST models forms the basis for the GS drive power. For the new system, however, some aspects of the engine have been modified. In order to allow long spring travel 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 30 degrees as on the F 800 S / ST. This solution has been made possible by a new design for the lower engine housing 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 and on the right. The GS engine has a modified clutch cover which creates more space in the footrest area; 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 models.
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 the boxer engines, which work with an identical firing offset. Most importantly, the even firing sequences create the best conditions for a balance load change with high torque yield.
Unique mass balance
The mass forces are offset by a balancing mechanism unique in series engine design. Instead of having conventional counterweight shafts, the oscillating mass forces are balanced by a joint system on the centre 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 rod 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 engine vibration when 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 which works without a 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. The engine oil in this area is constantly vacuumed 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 sup¬plies the lubricating oil system from this reservoir.
Camshafts matched to enduro requirements
The cylinders in the GS engines are fitted with a high-tech cylinder head.
As in the new K model range engines, 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 power reduction of the F 650 GS is via camshafts with different cams which reduce the lift and change valve timing. This results in a shorter valve overlap. 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 20,000km.
Mixture preparation
Other features typical of BMW include the mixture preparation, which is via a manifold injection with BMS-KP engine control and two, 46mm 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 petrol pump provides depending on the power requirement. The fuel system operates without return and only carries the quantity the engine actually needs. Because of this economical, patented regulation system
the fuel pressure can be modified over 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 rapidly warms up after a cold start and quickly starts its emission conversion function.
The air necessary to form the mixture reaches the new suction silencers via snorkels positioned in the cool air stream. The positioning well above the engine – which is advantageous during on and off-road riding – and the large volume, which supports torque, were made possible by positioning the fuel tank under the seat. While the suction snorkels of the F 800 GS are visible as a design element, in the F 650 GS they are concealed behind the front fairing.
