Inline-six engines have a staple in BMW’s automobiles for decades and the German manufacturer’s motorcycle division took on the challenge of adapting the straight-six to a bike without making it too long or too wide. The result is the BMW Motorrad Concept 6, and an evolution BMW says “will further expand the K-Series in the foreseeable future”.
The Concept 6’s engine is about four inches slimmer than BMW’s production inline-six engines, making it just a bit wider than a large-capacity four. To keep the width down, the engine has a relatively long stroke with very small gaps between cylinders. Electrical ancillaries and their drive components are positioned behind the crankshaft and above the transmission to further minimize engine width.
BMW engineers also tried to keep the weight low by using hollow-drilled camshafts and light connecting rods. The engine’s weight is also distributed so that a balance shaft and its drive elements are not necessary.
Like the straight-four in the K1300 series, the Concept 6’s engine is tilted forward 55 degrees for added balance and a low center of gravity. The tilted engine also provides space for an aerodynamically positioned intake manifold above the engine.
The Concept 6’s engine uses dry sump lubrication, keeping the crankcase low and flat. Without an oil sump, the engine can be placed lower in the frame than otherwise.
According to BMW, the six-cylinder engine produces power in the same range as its 1.3-liter straight four engines. The difference will be in the torque, which will be comparable to the largest motorcycle engines. BMW says will be the six-cylinder will offer 96 ft-lb. at 2,000 rpm with revs reaching nearly 9,000 rpm.
BMW describes the Concept 6 as a mix of classic and modern styling and an evolution of the café racer.
The “split face” design element found in other BMW bikes such as the S1000RR divides the Concept 6 into three sections, extending from the front of the fairing to the carbon-fiber fuel tank. LED headlights further accentuate the split face element.
Suspension is built around a light-alloy bridge frame with Duolever and Paralever arms for both front and rear. The 17-inch HP forged wheels are equipped with an extra-large brake system using six-piston fixec calipers.
The instrument panel uses a minimalist design without a rev counter. BMW says the rev counter was intentionally omitted because the engine produces a “supreme flow of power at all speeds”. Instead of a displaying the revs, the LED display shows how much torque is available.
EICMA 2009: Milan Motorcycle Show