Coolest Sportbikes of the ’90s: 1992 Honda NR750

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This amazing cutaway illustration of the NR750 accompanied <i>Cycle World</i>’s 1994 road test. (Cycle World Archives/)

For decades, Honda saw itself as motorcycling’s technology leader. The NR750 defined, in the metal, exactly what that meant to the company.

The entire concept of the NR goes back to the time between 1979 and 1981 and the NR500 Grand Prix racebike. That bike was a 499.5cc V-4 four-stroke with oval pistons that allowed eight valves per cylinder and eight total spark plugs. Its complexity and innovation ended up being its undoing. The monocoque chassis, 16-inch wheels, and the difficulty of matching the era’s potent two-strokes drove Honda to abandon the concept after two unsuccessful years of trial and error.

The racebike’s single-largest success was a 1981 heat-race win at Laguna Seca with Freddie Spencer aboard. If you can’t beat ‘em, join ‘em: Soichiro Honda despised two-strokes but was forced to develop them. First came the NS500 V-3 in ‘82; Spencer rode it to two wins in that year’s 500cc Grand Prix Championship and his first world championship the following year. In 1985, Honda debuted the era’s dominant 500 GP bike, the NSR500 V-4, which won nine world titles under Wayne Gardner, Eddie Lawson, Mick Doohan, Àlex Crivillé, and lastly Valentino Rossi.

From the original NR750 brochure, the bike is pictured with V-4 family members: the NR750 Endurance Racer (left rear) and 1979 NR500 (right front) and Kengo Kiyama’s NR500 (2X) racer that won the 1981 Suzuka 200-Kilometer Race (right rear). (Honda/)

But Honda wasn’t a company to give up a radical engineering concept simply because a simpler alternative had achieved unprecedented success. It was determined to make the oval piston work, and developed and built just around 700 street-legal NRs. At the time it was the most expensive production motorcycle Honda had ever sold, priced at a whopping $60,000.

The 748cc liquid-cooled 90-degree V-4 engine was of course the showstopper. At the time, Honda had around 200 patents on it. The reasons Honda had gone down this rabbit hole in the first place were cylinder-head flow and combustion efficiency; the elliptical pistons essentially gave the NR the combustion chamber volume of a V-8, allowing eight valves per cylinder (with gear-driven DOHC) to be tightly packed into the chamber. But making the pistons oval meant they were 30 percent smaller than a pair of pistons taking up the same space. This, according to Honda’s original NR brochure, resulted in a major reduction in sleeve-related friction. This quasi-V-8 required a lot of doubling down on components: twin connecting rods made of titanium (unheard of back then), two spark plugs, eight valves, and two EFI throttle bodies per cylinder. Getting rid of the gases was, of course, a complex labyrinth of an exhaust system in an 8-into-4-into-2-into-1-into-2 configuration.

This body-off shot shows the complexity hiding under all that plastic. (Honda/)

With all of this complexity, EFI was essential to feed the air-fuel mixture to the cylinders precisely. Honda’s PGM-FI fuel-injection system, as mentioned, had twin throttle bodies for each cylinder with a single injector in each bore. The system had a 16-bit ECU, a big deal for 1992, monitoring seven different sensors to optimize delivery.

For the August 1994 issue of Cycle World, we were able to find the only NR750 in the US. After much negotiation and legal deliberation with its movie director owner, we tested it. Our review said of the engine, “With an ultrashort stroke and incredible valve area, this motor lives to rev, but, ironically, spinning it to the sky-high 15,000-rpm redline is all but unnecessary. There is ample power right off idle, building progressively through the lower rev range, with a noticeable increase in output as the tacho needle sweeps through 7,500 rpm. From that point on up, power is linear and seamless.”

The NR750’s dash, with its mix of digital and analog gauges, was like nothing else on a production bike back in 1992. (Honda/)

Other items that were either production firsts, or adopted early before they became the norm, were a 45mm upside-down fork, twin four-piston Nissin brake calipers with 310mm discs up front, carbon fiber bodywork, side-mounted radiators, underseat exhaust, cassette-style transmission, a hybrid digital/analog dash, magnesium wheels measuring 16 inches in front and 17 inches at the rear, and cat-eye headlights with a projector-beam lamp on the left and a halogen flood on the right.

Back in 1992, Alan Cathcart got <i>Cycle World</i>’s first taste of the NR750 at Circuit Paul Ricard in France. (Cycle World Archives/)

As for the bike’s build quality, we said, “Without a doubt, the NR750 is the most finely finished production bike we’ve ever ridden. Attention to detail begins with its polished frame and swingarm, and doesn’t end once you delve beneath the immaculately finished carbon fiber–reinforced plastic bodywork. Not a solitary weld, fastener, or component appears cobby or misplaced. The engine itself is a magnificent sight to behold, looking more like a V-8 liberated from an IndyCar chassis than a motorcycle mill. Indeed the NR’s fuel-injected eight-valve oval cylinders are unique among motorized vehicles.”

Our remarkably gentle performance testing, dictated by the owner, produced less-than-earth-shattering results that were nevertheless still in line with production sportbikes of the era. The restricted British-spec bike we tested produced 108 hp at 14,000 rpm, with 47.7 lb.-ft. of peak torque coming at 10,750 rpm. Road Test Editor Don Canet eased the NR to a 11.71-second, 125.69 mph quarter-mile pass. For reference, the V-4-powered 1994 Honda VFR750 ran a 11.30-second/119 mph pass at the strip. Roll-on performance gave an indication of the engine’s midrange potential, producing a 4.7-second 40-to-60 mph time and a 4.8-second 60-to-80 mph time. Top speed was measured at 153 mph.

The August 1994 cover of <i>Cycle World</i>. (Cycle World Archives/)

There was a lingering irony to the NR, and in particular Honda’s obsession with four-stroke technology. When Grand Prix rules changed from two-stroke to four-stroke with the creation of MotoGP in 1992, Honda was staged and ready to go, completely dominating with Valentino Rossi on its 990cc RC211V V-5 in 2002 and 2003. Still, the complexity and expense of the oval-piston concept was just too much to overcome, and the technology faded into the past like so many other beautiful dreams.

“The NR is an art piece, a Fabergé egg of a motorcycle, destined more to a life of collecting dust than stone chips on its bellypan,” we said. “For fans of high-tech hardware, the 32-valve, oval-piston NR truly is the Holy Grail on Michelin TX radials.”

1992 Honda NR750 Specifications

MSRP:	$60,000 (1992)
Engine:	Liquid-cooled four-stroke V-4
Displacement:	748cc
Bore x Stroke:	75.3 x 42.0mm
Compression Ratio:	11.7:1
Transmission/Final Drive:	6-speed/chain
Cycle World Measured Horsepower:	108.0 hp @ 14,000 rpm
Cycle World Measured Torque:	47.7 lb.-ft. @ 10,750 rpm
Fuel System:	PGM-FI fuel injection
Clutch:	Wet, multiplate
Engine Management/Ignition:	Electronic
Frame:	Twin-spar aluminum
Front Suspension:	Showa 45mm inverted fork, fully adjustable; 4.7 in. travel
Rear Suspension:	Showa shock, fully adjustable; 4.7 in. travel
Front Brake:	Twin 4-piston calipers, 310mm discs
Rear Brake:	2-piston caliper, 220mm disc
Tires, Front/Rear:	130/70-16, 180/55-17
Rake/Trail:	24.5°/3.5 in.
Wheelbase:	56.6 in.
Ground Clearance:	5.2 in.
Seat Height:	30.4 in.
Fuel Capacity:	4.5 gal.
Cycle World Measured Wet Weight:	544 lb.

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