Honda NSR250R MC21 1990-1992 Service Manual

The MC21 generation, introduced for 1990, brought a genuinely different character to Honda's road-going NSR250R lineage. Compared to the outgoing MC18, the MC21 felt noticeably more compliant and forgiving at the limit — some riders at the time mistook that composure for the MC18 being the "sportier" chassis, when in reality the MC21's revised damping and Pro-Link geometry simply made it easier to go genuinely faster. 1990 also marked the first year Honda fitted a 17-inch rear wheel to the NSR250R, shod in a 150/60R17 Bridgestone Cyrox tire.

Power comes from the 249cc 90-degree V-twin two-stroke, liquid-cooled with crankcase reed valve induction and Honda's RC-Valve power-valve system, delivering a claimed 45 hp at 9,500 rpm and roughly 26 lb-ft of torque at 8,500 rpm through a 6-speed constant-mesh gearbox with a wet multi-plate clutch. A 41mm front fork offered preload adjustment only on base R models, with a non-adjustable rear shock — while the range-topping SP variant stepped up to preload and rebound damping up front, plus preload, rebound, and compression damping at the rear, paired with sportier Magtek wheels shod in Bridgestone Battlax rubber instead of the R model's Cyrox tires.

1991 introduced the SE model, essentially bridging the gap between R and SP: it carried the SP's desirable dry clutch and adjustable suspension without the full price premium, riding on the R model's Enkei alloy wheels. The rarest variant of all, the "Flash Colour Special" MC21-SP, was limited to just 900 units and finished in the high-saturation red developed for Honda's NR750, based on the 1992 All-Japan Road Race Championship works bike livery. Dry weight across the range sits around 291.8 lbs, with a 30.3-inch seat height and 16-litre fuel tank.