Integrated gearbox.

For the first time in the history of BMW Motorrad, the gearbox and clutch have been integrated in the engine housing on an opposed-twin engine gearbox. For the first time on an opposed-twin engine by BMW Motorrad, the cylinders are no longer screwed onto the crankshaft casing separately but are integrated directly. The two-part die-cast cylinder crankcase with a vertical parting line in the centre of the crankshaft is made of high-strength aluminium alloy. As a result, the two casing halves form a highly rigid bond made up of the cylinder and the bearing seat for the crankshaft. The cylinder with the water jacket has an open-deck construction. The bores are coated using the new electric arc spraying process via an electric arc with a low-wear and low-friction iron carbon alloy, as has previously been used in BMW car engines.

This design results in particular in benefits with respect to weight balance but also with torsion characteristics. As well as the compact, lightweight construction, the additional gearbox oil that was previously necessary for lubrication with the gearbox is no longer necessary. As before, high-strength helical cut splines are used on the gearwheels for gentle intermeshing, quiet running and better smoothness. And also as before, the gearbox shafts have anti-friction bearings on the new drive whereas the gear wheels (free gearwheels) run on needle bearings for low friction. The gearwheels and hence the gears are shifted via a selector drum made of steel mounted on ball bearings, three carburized switching forks with hard chrome-plated ends and sliding sleeves for a friction-locked connection of the gear wheel pairs.

The drive, which is used in the R 1200 GS for the first time and is the first series opposed-twin engine by BMW Motorrad, has a multi-disc oil bath clutch with eight friction discs in place of the previous single-disc dry coupling. The benefits of this solution are both less inertia torque due to the significantly lower exterior diameter of 147 millimetres (R 1200 GS previously: 180 mm) and a more compact design overall. For the first time on an opposed twin-engine, the clutch system is equipped with an anti-hopping mechanism. With this less engine braking torque is relayed to the rear wheel in overrun so that the motorcycle remains even more stable and safer-to-handle during braking.

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