1981 Yamaha YZ125
Specifications and workshop reference information for the 1981 Yamaha YZ125, 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
| Manufacturer | Yamaha |
| Model | YZ125H |
| Year | 1981 |
| Type | Motocross |
| Engine | Liquid-cooled 2-stroke single |
| Induction | Reed valve |
| Displacement | 125 cc |
| Bore x Stroke | 54.0 x 54.5 mm |
| Compression Ratio | 8.6–10.7:1 |
| Carburettor | Mikuni |
| Ignition | CDI magneto |
| Cooling | Liquid cooled |
Transmission
| Clutch | Wet multi-plate |
| Transmission | Constant mesh |
| Final Drive | Chain |
Dimensions
| Front Suspension Travel | 300 mm |
| Rear Suspension Travel | 315 mm |
Chassis
| Frame | Chrome-moly motocross frame |
| Front Suspension | Telescopic forks, 38 mm stanchions |
| Rear Suspension | Monocross single shock |
Brakes & Wheels
| Front Brake | Drum |
| Rear Brake | Drum |
Service Data
| Spark Plug | NGK BR9EG or equivalent |
| Spark Plug Gap | 0.5–0.6 mm |
125cc Other Specs
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