| | | | More details: BMW F800GS and F650GS |  Written: 26/11/2007 : 13:59. Read 10700 times (64/day). | | The integrality of this filed article is for Premium Members. | 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.
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The parallel twins’ drive comes from the F800 model series, but beyond this, the new enduro models have been completely redesigned: new frame and new wheel suspension with new spring-shock absorber elements. The previous model’s belt drive and single-strut swing arm have been replaced by a light chain drive in combination with a very stable and attractive aluminium profile, double-strut swing arm.
The new F 650 GS differs from its higher capacity variant by featuring a lower seat height, lower weight and slightly reduced engine power. 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.
The F800GS 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 liquid-cooled four-valve twin-cylinder 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. 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: 52kW / 71HP at 7, 000 min–1 and a maximum torque of 75Nm even at 4,500 min–1. 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.
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