Specs. Engine. 496.8cc, 80 deg., V-twin, pushrod actuated SOHC, 4 valves per cylinder BMW R 1250 RS . The R 1250 RS was launched in 2019 as a sportier variant to the R 1250 RT, with a 2021 BMW R 1250 RT Specifications. Engine & Drivetrain: Engine: Two-cylinder, air-/fluid-cooled, four-stroke boxer engine with two overhead spur-gear driven camshafts, one balancer shaft and BMW h4a4.