U‑turn to victory: the story of the Honda NSR500

In the latter years, four-stroke advocate Soichiro Honda had been fighting the rising tide of two-strokes by pure engineering: more cylinders, more revs, more elaboration. Since then, the oil-burning two-strokes had taken over all classes, with Yamaha eventually defeating MV Agusta’s 500cc fire engines in 1974.

Pops Honda had retired in 1973, but his dislike of the smoky strokers was part of the company’s DNA, and when the decision was taken to return to the World Championship series in 1979, it was with an extraordinary challenge. The two-stroke hegemony must be broken… with a four-stroke. A new generation of young engineers, all new to racing, was given the daunting task.

The result was one of the most interesting and technically adventurous grand prix motorcycles of all time. The NR500 (for New Racer – though it would be unkindly nicknamed “Never Ready”) foreshadowed several trends. It introduced so-called “inverted” telescopic forks, with the stiffer outer section at the top, where convention had it at the bottom. The NR also used the first slipper clutch, to minimise engine braking; a rising-rate rear suspension linkage; and carbon brakes. All of these are nowadays universal in MotoGP, and even some road bikes.

Other innovations were manifold. The fairing was the chassis, a hollow unit formed by joining two sheets of pressed aluminium. Honda technicians nicknamed it “clam-shell”. It served both to locate the front suspension and the motor, and also provided streamlining and protection for the rider.

It was light, stiff and clever, but very, very inconvenient. Even the simplest access to the motor, for example to change jets, required full disassembly. Engine, gearbox and rear suspension were extracted backwards out of the clamshell in one piece, after no less than 18 6mm bolts had been undone.

Years later, the head of engine development Suguru Kanazawa, who would later head Honda’s Swindon car plant, described the NR500 to me as “our teacher”. One lesson: a successful racing bike must be designed with ease of frequent access.

The most extraordinary feature was the engine. The maximum number of cylinders allowed was four, and Honda arranged them in a compact 90-degree vee. But what cylinders they were! They weren’t round.

To flow enough gas to combat the two-strokes, which fired twice as often, not only did the rev ceiling have to be beyond 20,000 rpm, but massive valve area was required. Honda achieved this with eight valves per cylinder, and to accommodate them, the pistons were flat-sided ovals, with two connecting rods apiece. You could describe it as a V8, but with only four cylinders.

The NR was a mighty achievement, demonstrating Honda’s independent (even pig-headed) thinking and unswerving integrity. And it had with the right horsepower numbers to take the fight to Suzuki and Yamaha.

Yet it was a mighty failure for all sorts of reasons. Embarrassingly, it barely qualified for its first GP, at Silverstone, in the presence of the retired founder Soichiro Honda. Fuelled for only a couple of demo laps, Takazumi Katayama managed that, but Mick Grant’s second bike crashed on the first corner, and caught fire. It was a debut as embarrassing as that of the BRM V16 29 years before, and at the same circuit.

When it failed to qualify for the next race at Le Mans, Honda withdrew to return in 1980, with not much more success.

There were many difficulties. Firstly, it was difficult even to start (GP races at the time had dead-engine push-starts), let alone ride. As one of the first riders Grant put it, “you had to be a bit of an athlete”.

Secondly, the power band was extremely narrow – between around 17,000 and 21,000rpm (tick over, with no flywheel, was 7,000rpm!). With a maximum of six gears allowed by regulations, this kept the rider very busy, while the torquier two-strokes were driving off the corners relatively calmly.

Thirdly, in its earlier phase, reliability was poor, and the rev-hungry engines required frequent replacement. Given the difficulty of access, this was a major task.

The NR500 never scored a single point, but might have achieved reliability and even success with further development. But it was too much of a gamble. Honda had to make a fresh decision.

If you can’t beat the two-strokes, then you must join them.

In fact, this U-turn had already been accomplished in motocross, where Honda had reluctantly embraced the fact that two-strokes were not merely lighter and easier to package, but also powerful, with a sharp throttle response, especially at lower revs. Gas flow limitations prevented them from revving very high, but there was no need.

Determined to do things their own way, Honda brought the motocross lessons to the grand prix tracks. Where rivals Suzuki and Yamaha had four-cylinder engines, Honda conceived a simpler V3. Not only was it lighter and more compact, it also had better low-end power, the reverse of Honda’s long-standing quest for high revs.

Honda had another trump card: a fresh-faced young American rider called Freddie Spencer. Fast Freddie and the NS500 proved a formidable combination, winning two races in their debut year of 1982, and in 1983 defeating reigning King Kenny Roberts and his Yamaha for Honda’s first premier-class title.

The NS was however a stop-gap in the factory’s quest for maximum horsepower, and was succeeded by what would become the definitive 500cc grand-prix two-stroke. The NSR500 would compete for the factory from 1984 until the 500s were supplanted by four-strokes in 2001 (and for another year for independent teams).

Typically, Honda did it differently. While the rivals were all moving towards V4 designs (actually, with twin cranks, more of a splayed square-four), the NSR had an in-line crankshaft, making it a wider but otherwise more compact motor. Over the years, the crankshaft would be split into two separate units, but still with the main bearings all in line. A true V4.

The first iteration showed that not all the NR’s lessons had been fully absorbed, however. Innovations included a belly-pan fuel tank, which suffered from surge and also meant that the CoG migrated upwards as the fuel load was burned off rather than (as is preferable) downwards. This left the four exhausts with large expansion chambers looping over the top of the engine, making access to the spark plugs and carburettors extremely difficult and uncomfortable. They toasted the rider’s chest into the bargain.

But the NSR evolved steadily. The fuel tank moved to the top, the exhausts to the bottom. The biggest step came with the so-called “Big Bang” close-firing-interval engine, introduced in 1992. This technology improves grip and tyre life by increasing the “rest period” between power impulses, and is another Honda innovation which has become universal in MotoGP, moving across also into the new-century four-stroke generation.

The NSR’s first championship went to Spencer in 1985, then Wayne Gardner in 1987, Eddie Lawson in 1989. In 1994 Mick Doohan began a five-year reign, followed by Alex Criville and then Valentino Rossi. The NSR won seven of the last eight two-stroke championships, bringing Honda’s total to 12 in 20 years, along with 12 constructor titles. Honda two-strokes won 146 GPs, all but 14 of them with the fin de siècle V4.

With its unique warbling drone, the NSR had achieved eventual domination of the 500 class. It was brutally fast as well as refined, reliable and rideable. It remains the ultimate icon of the breed.

FOS 2015 image by Alastair Staley.