All-New Liquid-Cooled Revolution X? Engine: The all-new liquid-cooled Revolution X engine that powers the Harley-Davidson Street? 500 motorcycle is 494 cc of genuine Harley-Davidson(R) V-twin built to thrive in high temperatures and heavy traffic. Liquid-cooling means it maintains temperature and performance. Bring on the stop-and-go traffic. The Street 500 stays cool and ready to respond instantly to your throttle hand. And you can count on this: every cubic centimeter of the 494 cc Revolution X engine is pure Harley-Davidson. 60-degree cylinders. 4 valves per head. And plenty of low-end torque. You don't have to be winding the RPMs up to five figures to feel the strength and character of this engine. It's built to give you a soul-satisfying ride at the kind of RPMs you find yourself riding at on city streets.