Both bikes use a totally new air-/oil-cooled, SOHC, 648cc, parallel-twin, four-valve-per-cylinder engine with a 270-degree crankshaft (à la Triumph Bonneville and Yamaha MT-07). The powerplant externally looks more retro than any other current “classic” bike, but inside there are plenty of modern updates, such as valve rocker arms that utilize rollers on the cam side and screw/locknut adjustable tappets on the valve side (for less friction and ease of maintenance), a power assist/slipper clutch, and a primary gear-driven clutch. Claimed power figures are modest, with 47 hp at 7,250 rpm and 38 pound-feet of torque at 5,250 rpm. I can already hear the spec-chart mavens now, “Only 47 hp?” Keep reading, please. Despite being air-cooled, the engines are clean enough to pass EPA and Euro 5 emissions standards, with RE claiming it will also pass Euro 6 standards when they come into effect in two years.