1975 Yamaha DT125B
Specifications and workshop reference information for the 1975 Yamaha DT125B, including engine, chassis, service data and setup details.
Note: Specs are compiled from factory data, manuals and owner feedback. Bikes vary — if yours is different, jump into the forum and share it.
General Specifications
| Engine Type | Air-cooled, 2-stroke, single-cylinder, piston port |
| Displacement | 123 cc |
| Bore × Stroke | 56.0 × 50.0 mm |
| Compression Ratio | 6.9:1 |
| Maximum Power | Approx. 12 hp @ 7500 rpm |
| Maximum Torque | Approx. 14 Nm @ 7000 rpm |
| Carburetor | Mikuni VM24 |
| Lubrication | Autolube oil injection |
| Fuel Mix Ratio | N/A (oil injection) |
| Ignition | Magneto (points) |
| Spark Plug | NGK B7ES |
| Spark Plug Gap | 0.6 – 0.7 mm |
Transmission
| Transmission Type | 5-speed manual |
| Clutch | Wet multi-plate |
| Primary Reduction | Approx. 3.409 |
| Final Reduction | Approx. 3.000 |
| Overall Reduction | Varies by gear |
Dimensions
| Overall Length | Approx. 2050 mm |
| Overall Width | Approx. 820 mm |
| Overall Height | Approx. 1100 mm |
| Wheelbase | Approx. 1320 mm |
| Ground Clearance | Approx. 240 mm |
| Fuel Tank Capacity | Approx. 8.0 L |
Chassis
| Frame Type | Steel tubular, double cradle |
| Caster Angle | Approx. 28° |
| Trail | Approx. 110 mm |
| Front Suspension | Telescopic fork |
| Rear Suspension | Twin shock swingarm |
| Front Suspension Travel | Approx. 170 mm |
| Rear Suspension Travel | Approx. 100 mm |
Brakes & Wheels
| Front Tire | 2.75-21 |
| Rear Tire | 3.50-18 |
| Front Brake | Drum |
| Rear Brake | Drum |
125cc Other Specs
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