| MODEL | YAMAHA DT 125 1978 |
| Year | 1978 |
| Engine Type | Two stroke, single cylinder, reed-valve |
| Displacement / Capacity | 123 cc / 7.5 cu in |
| Bore X Stroke | 56 x 50 mm |
| Compression Ratio | 7.2:1 |
| Cooling System | Air cooled |
| Max Power | 9.5 kW / 13 hp @ 7000 rpm |
| Max Torque | 13.3 Nm / 9.8 lb-ft @ 6500 rpm |
| Ignition | Magneto |
| Induction | Single 24 mm Mikuni carburettor |
| Start System | Kick |
| TRANSMISSION SPECS | |
| Lubrication | Autolube (1.2 Litres / 1.76 qts oil capacity) |
| Gear Box | 6 speed |
| Clutch | — |
| Final Drive | Chain |
| CHASSIS SPECS | |
| Frame | — |
| Front Suspension | Telescopic forks |
| Rear Suspension | Monocross |
| Front Brakes | Drum |
| Rear Brakes | Drum |
| DIMENSION SPECS | |
| Overall Length | 2095 mm / 82.5 in |
| Overall Width | 866 mm / 34.1 in |
| Overall Height | 1120 mm / 44.1 in |
| Seat Height | 810 mm / 31.9 in |
| Wheelbase | 1404 mm / 55.3 in |
| Ground Clearance | 265 mm / 10.4 in |
| Dry Weight | 96 kg / 212 lbs |
| Wet Weight | — |
| WHEEL SPECS | |
| Front Tyre | 2.75-21 |
| Rear Tyre | 3.50-18 |
| FUEL SYSTEM | |
| Fuel Capacity | 6.8 Litres / 1.8 US gal |
| Fuel Consumption | — |
| Top Speed | — |
The 1978 model year carried over the 1977 Monocross DT125 with the same engine and chassis figures on the database page. A light air-cooled trail two-stroke with a six-speed gearbox and drum brakes.
