Honda NS400R 1985-1987 Service Manual

Bennetts' own retrospective calls the NS400R "an exquisitely engineered V3 two-stroke triple, now the bargain of the factory '500' replicas" — a genuine street-legal homage to Freddie Spencer's championship-winning NS500 GP racer, built after Honda's engineers won an internal argument to pursue two-stroke development despite the company's traditional four-stroke racing heritage. It stands as Honda's largest-displacement street-legal two-stroke ever produced, with just 12,000 units built across the full run, including a limited UK allocation of only 300 machines in 1985 split between tri-colour and Rothmans replica liveries.

Power comes from a 387cc liquid-cooled 90-degree V3 two-stroke — bore and stroke stretched from the earlier MVX250F's 47mm x 48mm to 57mm x 50.6mm, with strengthened cases and internals addressing the reliability problems that had plagued that predecessor. Nikasil-coated cylinders, among the earliest production use of the technology, delivered a claimed 72 hp at 9,500 rpm and roughly 37-39 lb-ft of torque at 8,000 rpm, fed by triple 26mm Keihin flat-slide carburetors and Honda's GP-derived ATAC (Auto-controlled Torque Amplification Chamber) system on the front two cylinders, boosting power delivery across the rev range. A 6-speed transmission with wet clutch and chain final drive rounded out the drivetrain.

Bennetts' testing found the box-section aluminum perimeter frame gave the NS400R sharper handling than either the Suzuki RG500 or Yamaha RD500LC — many period testers considered it the finest-handling street bike on the market at the time. At just 163kg dry, only 16kg heavier than the smaller NS250R despite the extra displacement, the chassis flicked from side to side with genuine ease. Front suspension used air-assisted 37mm telescopic forks with TRAC anti-dive control wrapped in distinctive aerodynamic shrouds, paired with a rising-rate Pro-Link rear shock offering remote preload adjustment via a knob under the left side panel — genuinely state-of-the-art hardware for 1985. Dual 256mm front discs and a single 220mm rear disc, both with 2-piston calipers, handled braking. Only two production years existed in practice — the 1985 R-F and 1986 R-G — identical apart from model-year badging, before the range wound down through 1987.