| MODEL | YAMAHA WR 400F 1998 - 2000 |
| Year | 1998 - 2000 |
| Engine Type | Four stroke, single cylinder, DOHC, 5 valve |
| Displacement / Capacity | 399 cc / 24.3 cu in |
| Bore X Stroke | 92.0 x 60.1 mm |
| Compression Ratio | 12.5:1 |
| Cooling System | Liquid cooled |
| Max Power | 35.3 kW / 48 hp @ 8000 rpm |
| Max Torque | 39 Nm @ 7500 rpm |
| Ignition | CDI |
| Induction | 39 mm Keihin FCR carburettor with accelerator pump and throttle position sensor |
| Start System | Kick |
| TRANSMISSION SPECS | |
| Lubrication | — |
| Gear Box | 5 speed |
| Clutch | — |
| Final Drive | Chain |
| CHASSIS SPECS | |
| Frame | — |
| Front Suspension | 46 mm inverted Kayaba fork, 300 mm / 11.8 in travel |
| Rear Suspension | Kayaba Monocross, 315 mm / 12.4 in travel |
| Front Brakes | Single 245 mm disc, 4-piston caliper |
| Rear Brakes | Single 220 mm disc, 2-piston caliper |
| DIMENSION SPECS | |
| Overall Length | — |
| Overall Width | — |
| Overall Height | — |
| Seat Height | 991 mm / 39.0 in |
| Wheelbase | 1480 mm / 58.3 in |
| Ground Clearance | 373 mm / 14.7 in |
| Dry Weight | 114 kg / 251.3 lbs |
| Wet Weight | — |
| WHEEL SPECS | |
| Front Tyre | 80/100-21 |
| Rear Tyre | 110/100-18 |
| FUEL SYSTEM | |
| Fuel Capacity | 8 Litres / 2.1 US gal |
| Fuel Consumption | — |
| Top Speed | — |
The first four-stroke WR, derived from the YZ400F motocrosser and the model that made four-strokes credible in enduro. Its five-valve engine was praised for strong mid-range pull, and for 2000 it received a slimmer seat and tank from the YZ426F. It had no electric start and no trip meter as standard.
