| MODEL | YAMAHA DT 125MX 1980 |
| Year | 1980 |
| 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 | 10.3 kW / 14 hp @ 6500 rpm |
| Max Torque | 15.2 Nm / 1.5 kgf-m @ 6500 rpm |
| Ignition | Flywheel magneto |
| Induction | Single 24 mm Mikuni carburettor |
| Start System | Kick |
| TRANSMISSION SPECS | |
| Lubrication | Autolube (0.9 Litres oil capacity) |
| Gear Box | 6 speed |
| Clutch | Wet multiplate |
| Final Drive | Chain |
| CHASSIS SPECS | |
| Frame | — |
| Front Suspension | Telescopic forks, 160 mm / 6.3 in travel |
| Rear Suspension | Monocross, 115 mm / 4.5 in travel |
| Front Brakes | Drum |
| Rear Brakes | Drum |
| DIMENSION SPECS | |
| Overall Length | 2080 mm / 81.9 in |
| Overall Width | 885 mm / 34.8 in |
| Overall Height | 1120 mm / 44.1 in |
| Seat Height | 855 mm / 33.7 in |
| Wheelbase | 1325 mm / 52.2 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 | 7 Litres / 1.5 US gal |
| Fuel Consumption | 79 mpg |
| Top Speed | 74 mph / 119 km/h |
The DT125MX was a restyled air-cooled Monocross trail bike with a slightly stronger 14 hp engine and long-travel suspension. It was a road-legal learner-class dirt bike with drum brakes and a six-speed box.
