BMW motorcycle design has changed little in the decades immediately following World War II. In 1970, the marque walked away from its antiquated Earles-fork bikes, redesigning its entire catalog. The result was the line known as Slash 5—telescopic forks, 12-volt electrics (replacing 6-volt), bright new colors (replacing black and white and not much else), and, chiefly, a new range of engines. BMW’s 1970 engines looked much like the ones sold in 1969—two horizontally opposed and air-cooled cylinders, an alloy crankcase, pushrods carried in external tubes, and peanut-shaped valve covers—but the new units were a complete rethink, aimed at greater output with no sacrifice in durability. As such, their combustion chambers and pistons bore a significant resemblance to the strong and potent straight-sixes used by contemporary BMW cars.