The Honda NSR250 – Two-Stroke MotoGP Madness For The Masses Part 3

The Honda NSR250 – Two-Stroke MotoGP Madness For The Masses Part 3

Enter the NSR250. This new model shared no parts with the NS250, and had pretty much been redesigned from the ground up. The only totally identical items were the nickel-silicone carbide (Nikasil) coated aluminum cylinders, hi-tech for the time, for reduced friction and increased wear resistance. Again, the motor, a 90 degree liquid-cooled V twin, with a valve reed intake system and 28mm flat slide carburetors, was almost a clone of the NSR models that were cleaning up in the Grand Prix. The engine design was cutting edge, and the redesigned carburetors, sitting parallel to the tops of the cylinders to feed directly into the crankcase, as well as the cassette-type gearbox (allowing quick removal of the gearbox without opening the motor up) were all taken straight from the race bike. Also revolutionary was the new RC (Revolutionary Control) powervalve system.

The styling too was lifted straight off the GP bikes, featuring a split-level seat with a pillion seat color-matched to the paintwork to make it look like a solo-seat race bike. This model was dubbed the MC16 in the Honda factory, and put out an impressive 45 horsepower at 9500rpm. The fact that it put out “only” 45 horsepower was actually due to Japanese laws about engine size and horsepower; The Man in Japan said no-no to 250cc bikes putting out more than 45 horsepower. Derestricting the bike was easy enough, though, and once derestricted the NSR250 MC16 put out a healthy 55 horsepower.

MC21 1990 Promo Image

One of the big improvements over the NS250 was a loss of weight; the ’80s obsession with aerobics and fighting flab had crossed over into the motorcycling world, it seems; throughout the decade, all of the main manufacturers fought tooth and nail, like a room full of desperate Biggest Loser contestants, to see who could drop the most weight from their machines. With Honda’s MC16 weighing in at just 125kg (275lb) dry, a substantial saving over its predecessor, the power-to-weight ratio was astonishing, and translated into blistering acceleration and beautifully flickable handling. This, combined with the Honda’s striking “fighting” red and white and (later) blue and white “Terra” color schemes, made the new NSR250 MC16 the best selling sports 250 in Japan in 1986.

The other manufacturers were determined not to be left out of this two-stroke revolution, though. Yamaha had debuted their TZR250 – a more street-oriented, less race rep bike – in 1986, while Suzuki continued to develop their RG250 Gamma, which would later evolve into the legendary RGV250. Kawasaki, however, seemed to be focusing their R&D attention on big four-strokes (as they had no two-stroke racers on which to base a street-oriented race rep). Kawasaki couldn’t help but notice how wildly popular the 250 two-stroke race rep category was becoming in Japan, though, and eventually realized that it would be foolish not to tap into the hype. They released their KR1 – a parallel twin, unlike the TZR, NSR and RGV – in 1988, which they would upgrade to the KR1S in 1990, rarest of the 250 race reps, which would also earn the title of fastest production 250 ever built – more on that in another article, though.

MC21-SP 1990 Promo Image

The ’80s were a decade of rapid technological advancement in many fields, and the breaking of all sorts of boundaries. In 1980, computers could be accessed only in universities and tech labs, and most ordinary people had never seen, let alone used one. By the early ’90s, just twelve or thirteen years later, most first world homes had a PC running Windows 3.1 (or an Apple, if you wanted to be different). The tech war of the decade spilled over to the motorcycle world, and the Japanese domestic market represented the front line of these battles. Frantic development on the NSR250 continued with the release of the 1988 MC18 model, which was a complete redesign of the machine from the ground up. Computers were now making their way into the auto world, and the NSR250 MC18 featured a computer-controlled carburetion system called the PGM system – the first computer-controlled system ever fitted to a production two-stroke motorcycle.

The three spoke alloy rims were changed to the signature Honda six spoke rims, with rear tire width increasing to a 130 profile. The aluminum frame and swingarm were thicker and stiffer while remaining just as light, while the forks became beefier at 41mm. Suspension was upgraded, with more adjustability. The styling was more slick and modern, again taking cues from the race machine on which it was based – and the speedo and warning light cluster were easily detachable (leaving only the tachometer) for racing. Initial color schemes stayed the same, even though the entirety of the bodywork was different from the MC16, featuring the same classic Terra blue and white and fighting red and white, although a gray, silver and black pattern was also introduced in 1989.

MC21-SE 1992 Promo Image

The motor was upgraded too. While retaining the same configuration, the size of the carburetors was increased to 32mm, and engine power was up – 63 horsepower in derestricted form, and even peakier than the MC16. The ultra-advanced computer-controlled PGM unit provided superb engine management, with a three dimensional map tied to ignition timing, throttle position and motor rpms. The powervalves were also upgraded for better performance at all rpm. Owing to an increase in high speed, often fatal motorcycle accidents in Japan, the NSR250 (and, in fact, pretty much any motorcycle produced for the Japanese domestic market) was limited to a top speed of 180km/h (112mph) – which, again, was fairly easy to get around if you knew how.

The MC18 was also the first of the NSR series to produce an SP (Sports Production) model, aimed at amateur racers who competed in a popular production racing class in Japan using unmodified, commercially available bikes. In 1988, the NSR250SP dominated this class. The SP version featured ultra-lightweight magnesium wheel rims and a stunning Rothmans paint job that echoed that of the MotoGP bikes. Only 300 were produced, and are therefore exceedingly rare and valuable today.

The ’89 MC18 received a few minor upgrades; wider profile tires (150 at the rear), slightly revised bodywork, high-set, upswept silencers, a remapped PGMII system (for better street performance and increased fuel efficiency) and upgraded rear suspension. The SP version got adjustable suspension, both front and rear, as well as a dry clutch and magnesium wheels, as before.

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