oval piston

The oval piston concept continued in the NR750 endurance bike, which made a brief appearance during the 1980s.

The oval piston concept allowed for eight valves per cylinder which generated more power due to the increased air/fuel mixture throughput and compression.

This was achieved by designing an oval piston that allowed a total of 8 valves per cylinder, and connecting two con-rods to each piston.

Whereas the NR500 had used an oval piston with straight sides, the road going NR750 used an elliptical piston with curved long sides.

The NR500 GP bike was designed for a quixotic battle against the dominant two-strokes, its inherent four-stroke power disadvantage countered by the use of oval pistons and eight valves for each of the V4's cylinders.

Guzzi retired from racing at the end of the year and the fascinating V8 motorcycle disappeared from the race circuit, never to be equaled, although Honda has tried with the oval piston NR500 which was even less of a success and a 4 cylinder at that.

The bike had a 750 cc V4 with oval pistons, utilising 8 valves per cylinder and 2 conrods per piston; the design allowed the engine to meet FIM racing regulations limiting the number of cylinders to 4, while providing the valve area (and therefore increased efficiency) of a V8.