The Honda NR750 was the first production motorcycle to use Honda’s oval-piston V4 engine.
Honda developed oval pistons for its NR racing project in the late 1970s and 1980s. The unusual shape allowed each cylinder to use eight valves and two connecting rods, aiming to combine the breathing advantages of many valves with the compact layout of a V4 engine.
The road-going NR750, introduced in 1992, was a highly exclusive motorcycle produced in limited numbers. It used a 747 cc V4 engine and was famous for its engineering complexity, carbon-fiber bodywork, and distinctive under-seat exhaust outlets.
The NR750 is often confused with the RC30 or RC45, Honda’s more conventional V4 racing homologation motorcycles. Those models used round pistons; the NR750’s defining feature was its oval-piston engine.