Honda NR750 – RC40 strange oval piston-piston

Honda NR750 (RC40)

With Ian Falloon

Honda has a long history of making some of the weirdest motorcycles that have ever graced the planet, but many of these are for racing only and not for the general public, not even those who don’t. most connoisseur. But in 1992, that all changed with the introduction of the Honda NR750, which was the first and only opportunity for customers to experience Hondas achievement with oval piston technology.

Unfortunately, by the time the NR750R was released, the oval piston cylinders had been outlawed by the FIM, so the NR750R was always a novelty. In the end, instead of creating a track replica, Honda marketed the NR750 as an extremely expensive collector’s bike.

Although based on the 1987 endurance racing NR750, the production engine is different in that it is a 90-degree V-4 (like the RC30) and not a racer’s 85-degree one.

Apparently a V8 with four pairs of cylinder-mounted cylinders to bypass the FIM regulations banning V8s, pistons measuring 101.2 x 50.6 mm and stroke 42 mm, giving capacity 747.7 cc.

Inside the engine is a wealth of special components, from eight titanium control rods to nickel-plated and Teflon-coated pistons. Each piston ring requires 27 machining operations, the spark plugs are 8 mm and the 8 30 mm chokes have a single fuel injector.

A departure for Honda is the incorporation of the PGM-F1 electronic fuel injection system. Fully mapped, with seven sensors and a 16-bit CPU, this also includes self-diagnosis.

Also included in the odd spec is a gear-driven twin camshaft, eight valves per cylinder, set at an included angle of 29 degrees, and with a compression ratio of 11.7:1 and 8 to 4. 2 into 1 -Into-2 stainless steel exhaust system with a capacity of 125 horsepower at a very moderate engine rpm of 14,000 rpm.

Power could easily be increased to more than 140 hp but Honda decided to limit power to improve longevity and drivability, arguing that rider comfort and controllability are more important than power. absolute on the track.

The NR750R chassis is more conventional than the engine, with a conventional aluminum beam frame and single-sided swingarm. The front fork is a 45mm upside-down Showa, and specially designed 16- and 17-inch wheels. Honda even asked GP partner Michelin to develop a specific type of radial tyre, specifically a 16-inch 130/70ZR front tire that claims to offer the same rolling circumference as a regular 17-inch front tyre.

Even by modern standards, chassis specs are up to par, Showa suspension offers comparable compliance and responsiveness to units a decade into the future, while discs 310 mm floating front with four-piston brake calipers provides more than enough stopping power for the NR750 heavy bike.

With a weight of 222.5 kg and a wheelbase of 1,435 mm, the NR750 will never be a slim sportster. But it is crafted with the most incredible attention to detail and crafted from the highest quality materials.

The carbon fiber body panels are individually handcrafted to each set of numbers, the flaps conceal the side racks when it’s folded, and the saddle is finished in crepe urethane. Even the custom-made nickel silver and carbon fiber ignition key emphasizes the oval piston concept.

No detail has been overlooked and the production is extremely limited, only 322 pieces. 220 were built in 1992 and 102 more in 1993, each requiring a 25% deposit and built to order on a first-come, first-served basis, and they were officially sold only in Japan and Europe.

While the NR750 isn’t the high-performance superbike people expect from Honda, it’s in many ways the world’s last truly high-tech motorcycle. More comfortable than a superbike, it also offers excellent handling and braking, along with impressive styling.

Even with the outrageous and extraordinary price tag, buying an NR is more than simply buying an expensive exotic item. With the NR you’ve bought into a 13 year legacy oval piston and piece of mechanical history. Over twenty years the NR750’s appeal hasn’t waned, and if the price of used examples is anything to do with it, it’s become all the more revered for its attractive and appealing engines. conductive power supply for it.

Five things about the NR750 and Hondas oval pistons

1. The NR750’s engine isn’t the only groundbreaking feature. It is the first Japanese sports car to feature fully mapped EFI and the first from any country to use upside-down front forks, carbon fiber bodywork, side-mounted radiators and exhaust pipe under the saddle. Another first was a digital speedometer.
2. Honda’s first oval piston rod was the ill-fated NR500. Intended to match the current 500cc two-stroke Yamahas and Suzukis, the race made its debut at Silverstone in August 1979 but neither model qualified.
3. After throwing everything into the development of the NR500, the improved 2X arrived in 1982. At 22,000 rpm, rising star Freddie Spencer defeated world champion Kenny Roberts in a showdown. hot race for the Laguna Seca 200.
4. Undeterred by the NR500’s debacle, Honda turned their attention to a 750cc oval piston endurance racer. Participating in the 1987 Le Mans 24-hour race, Australia’s Malcolm Campbell made it to the second-fastest qualifying round. During the race, the NR750 lasted only three hours, until a large latch loosened, blocking the oil line and holding a piston tight. The NR750 then appeared in the 1987 Swann series. Now producing 160 hp, Campbell won a race and finished third overall.
5. Since the NR750 cannot be considered a racing equivalent, Honda prepared a record-breaking 180 kg, 155 hp machine for Loris Capirossi to drive at the Nardo test track in southern Italy. In August 1992, Capirossi set new air-mile, flight-mile and vertical-start mile records and 10 km, with the fastest speed being 299,825 km/h.

Specifications Honda NR750

• Engine displacement – 747.7 cc
• Engine layout – 90 degrees V-four
• Diameter – 101.2 x 50.6 mm (Equivalent to 75.3 mm in circular shape)
• Travel – 42 mm
• Compression ratio – 11.7:1
• Valves – Cam, DOHC gas-operated, eight valves per cylinder
• Engine weight – 80.5 kg
• Touch – PGM FI, throttle body 8 x 30 mm
• Ignition – Computer controlled digital transistors with electronic application
• Clutch – wet, multi-plate, hydraulic
• Gearbox – Six-speed
• Total oil capacity – 4.7 liters
• Oil capacity at oil/filter change – 3.9 liters
• Oil Type – 10W-40
• Frame – Double tube with three square cross section
• Wheel Angle – 24deg 30′
• Trail – 88 mm
• Front suspension – USD telescopic fork, travel 120mm
• Rear suspension – Longitudinal asymmetrical Pro-Arm swingarm with Pro-Link, 120 mm travel, nitrogen-charged piggyback shock absorbers
• Rims – Magnesium Alloy, 16 × 3.5″ (F), 17 x 5.5″ (R)
• Tires – 130 / 70-16 (F), 180 / 55-17 (R)
• Front brake – 310 mm dual disc, four-piston caliper
• Rear brake – 220 mm ventilated disc, dual piston calipers
• Fuel tank capacity – 17 liters
• Length x Width x Height – 2150 x 700 x 1190 mm
• Wheelbase – 1435 mm
• Seat height 785 mm
• Ground clearance – 130 mm
• Dry weight – 223 kg
• Restraint / Wet Weight – 244 kg

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