It began back in 1979 with the introduction of the NR500 grand prix racebike. Rather than fielding a 500cc two-stroke engine, Honda used a four-stroke oval-piston V-4 motor – essentially a V-8 with four cylinders that could be revved to 19,500 rpm! The oval cylinder area was so large that it used eight valves in each cylinder!
The First Honda V4
1987 NR750 pistons:
OEM Honda's V4 Heritage (Click the drop down to "V4 Heritage")