| MODEL | YAMAHA RD 125 1978 |
| Year | 1978 |
| Engine Type | Two stroke, parallel twin |
| Displacement / Capacity | 124 cc / 7.6 cu in |
| Bore X Stroke | 43 x 43 mm |
| Compression Ratio | 6.8:1 |
| Cooling System | Air cooled |
| Max Power | 12.4 kW / 17 hp @ 8500 rpm |
| Max Torque | 1.3 kgf-m @ 8000 rpm |
| Ignition | Battery coil |
| Induction | 2x 18 mm Teikei carburetors |
| Start System | Kick |
| TRANSMISSION SPECS | |
| Lubrication | — |
| Gear Box | 5 Speed |
| Clutch | — |
| Final Drive | Chain |
| CHASSIS SPECS | |
| Frame | Steel tube, engine used as a stressed member |
| Front Suspension | 28 mm telescopic forks |
| Rear Suspension | Dual shocks, preload adjustable |
| Front Brakes | Single 240 mm disc |
| Rear Brakes | 130 mm drum |
| DIMENSION SPECS | |
| Overall Length | — |
| Overall Width | — |
| Overall Height | — |
| Seat Height | 749 mm / 29.5 in |
| Wheelbase | 1245 mm / 49.0 in |
| Ground Clearance | — |
| Dry Weight | — |
| Wet Weight | 115 kg / 255 lbs |
| WHEEL SPECS | |
| Front Tyre | 2.75-18 |
| Rear Tyre | 3.00-18 |
| FUEL SYSTEM | |
| Fuel Capacity | 11.5 Litres / 3.04 US gal |
| Fuel Consumption | — |
| Top Speed | — |
The 1978 RD125 continued with the same listed specification: air-cooled parallel twin, five speeds, front disc brake and rear drum. It remained a light, affordable entry-level two-stroke.
