 Honda's race bikes were known for their "sleek & stylish design" and exotic engine configurations, such as the 5-cylinder, 22,000 rpm, 125 cc bike and their 6-cylinder 250 cc and 297 cc bikes.In 1979, Honda returned to Grand Prix motorcycle racing with the monocoque-framed, four-stroke NR500.The FIM rules limited engines to four cylinders, so the NR500 had non-circular, 'race-track', cylinders, each with 8 valves and two connecting rods, in order to provide sufficient valve area to compete with the dominant two-stroke racers.