| MODEL | YAMAHA RD 400E 1977 |
| Year | 1977 |
| Engine Type | Two-stroke, parallel twin, reed-valve torque induction |
| Displacement / Capacity | 398 cc / 24.2 cu in |
| Bore X Stroke | 64 x 62 mm |
| Compression Ratio | 6.2:1 |
| Cooling System | Air cooled |
| Max Power | 32.3 kW / 44 hp @ 7500 rpm |
| Max Torque | 41.1 Nm / 4.2 kgf-m @ 7000 rpm |
| Ignition | Battery, dual coils, breaker points |
| Induction | 2 x 28 mm Mikuni carburettors |
| Start System | Kick |
| TRANSMISSION SPECS | |
| Lubrication | Autolube |
| Gear Box | 6-speed |
| Clutch | Wet multiplate |
| Final Drive | Chain |
| CHASSIS SPECS | |
| Frame | — |
| Front Suspension | Telescopic forks |
| Rear Suspension | Swingarm, dual shocks |
| Front Brakes | Single 267 mm disc |
| Rear Brakes | Single 267 mm disc |
| DIMENSION SPECS | |
| Overall Length | 1995 mm / 78.5 in |
| Overall Width | 760 mm / 29.9 in |
| Overall Height | 1060 mm / 41.7 in |
| Seat Height | 800 mm / 31.4 in |
| Wheelbase | 1320 mm / 51.9 in |
| Ground Clearance | 150 mm / 5.9 in |
| Dry Weight | 165.5 kg / 364.8 lb |
| Wet Weight | 171 kg / 376 lb |
| WHEEL SPECS | |
| Front Tyre | 3.00S-18 |
| Rear Tyre | 3.50S-18 |
| FUEL SYSTEM | |
| Fuel Capacity | 16.5 Litres / 4.3 US gal |
| Fuel Consumption | 43 mpg |
| Top Speed | 172 km/h / 106.8 mph |
The 1977 RD400 continued the air-cooled 398 cc reed-valve twin with a six-speed gearbox and disc brakes front and rear. Period road tests praised its light weight and performance but noted very sensitive throttle and brake response, some vibration, and slower than expected quarter-mile times.
