In 1990 Suzuki presented a whole new Suzuki GSX-R400 (new internal model code GK76A) with inverted forks and many other modifications. The frame was upgraded from twin spur to double cradle, similar to the 1988 Suzuki GSX-R750 model change.
A new 4 into 1 exhaust increased the engine power close to 60bhp and the engine redlined at 14,500 rpm. Nissin 4-cylinder front brake calipers, new fairing design with faired-in headlights, preload-adjustable forks, unbraced swing-arm, rear hugger mudguard.
1989 Full model change as a direct machine of F-3 champion machine Suzuki GSX-R400R and TTF-1 champion machine Suzuki GSX-R750. The engine which was set to 24 degrees ante leaning by 8 degrees more than the 1989 model is a completely new design.
Especially the valve train system was thoroughly reviewed, and it showed 4.0kgm/10,000rpm by weight saving and adoption of 1 valve 1 rocker arm. The increased heat measures with high performance are supported by water-cooled oil cooler and radial flow radiator. The frame became an aluminum double cradle with the same layout as the TTF-1 machine and durable racer, and the inverted mode was adopted for the front fork.
Suzuki GSX-R400 1990 Specifications
SP model Blue/White
Dimensions and dry mass
Type (frame code): GK76A
Overall length: 1,995 mm (78.5 in.)
Overall width: 710 mm (28.0 in)
Overall height: 1,060 mm (41.7 in)
Wheelbase: 1,435 mm (56.5 in)
Ground Clearance: 125 mm (4.92 in.)
Seat height: 735 mm (28.9 in.)
Dry mass (weight): 167 kg (367 lbs)
Engine type: Water-cooled DOHC inline-4, 16 valves
Bore x stroke: 56,0 mm x 40,4 mm (2.205 x 1.591 in.)
Piston displacement: 398 cc
Compression ratio: 11,8 :1
Maximum power: 59 hp/ 12,000 rpm
Maximum torque: 4,0 kg-m/ 10,000 rpm
Top speed: about 200 km/h (124 mph)
Starting system: Electric starter
Lubrication system: Wet sump
Carburetor: Mikuni 27mm x 2