1200 CC two-cylinder opposed-twin engine
Our two-cylinder opposed-twin engines are bursting with character and embody BMW in a way that has been admired for more than 8 decades now – superior, high-performance and robust. The current generation is even more powerful, lighter, more refined and ensures even lower consumption than before. With its air/oil cooling and four-valve technology, the engineering principle of the new double overhead camshaft two-cylinder opposed-twin engine is akin to traditional BMW Motorrad two-cylinders – and yet still constitutes an entirely new development.
Designed for higher speeds, the new opposed-twin engine has two chain-driven, overhead camshafts (DOHC) for each cylinder with valves actuated by extra light, high-speed roller followers. The radial arrangement of the four valves has enabled a highly compact combustion chamber design. As with the predecessor model, the mixture is ignited via two spark plugs. The previous compression ratio of 12.0:1 has also been maintained while knock control enables use of Super (plus) fuel with 95-98 RON. The nominal load capacity has been determined as 98 RON.
The horizontal arrangement of the camshafts in the direction of travel on the new opposed-twin engine has resulted in two special technical features. Each camshaft controls one intake and exhaust valve and the cams are tapered due to the radial arrangement of the valves. Intake and exhaust control times for the two camshafts have been optimized for particularly vigorous unleashing of power in the lower and central speed range and with greater revving power at the same time.
Compared to the predecessor model, the diameters of the valve heads have been enlarged on the intake side from 36 to 39 millimeters and on the exhaust side from 31 to 33 millimeters. Valve play has been compensated for using light hemispherical shims. Opening strokes have been increased on the intake and exhaust side from 10.54 and 9.26 millimeters previously to 10.8 millimeters for a greater free valve cross-section. All this makes for an engine with a superior character that is a model of outstanding dynamics and sheer joy of revs, something it demonstrates impressively starting from even the very lowest of speeds.