1991 Yamaha YZ125 Specifications and Specs
Specifications and workshop reference information for the 1991 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
| Engine Type | Single-cylinder, liquid-cooled, reed valve, 2-stroke |
| Displacement | 124 cc |
| Bore × Stroke | 54.0 mm × 54.5 mm |
| Compression Ratio | 8.5:1 |
| Maximum Power | 35 hp @ 11,000 rpm |
| Maximum Torque | 21.5 Nm @ 10,000 rpm |
| Carburetor | Mikuni TM35SS |
| Lubrication | Premix |
| Fuel Mix Ratio | 32:1 |
| Ignition | CDI |
| Spark Plug | NGK BR8ES |
| Spark Plug Gap | 0.7 - 0.8 mm |
Transmission
| Transmission Type | 6-speed constant mesh |
| Clutch | Wet multi-plate |
| Primary Reduction | 3.409 (58/17) |
| Final Reduction | 3.846 (50/13) |
| Overall Reduction | 11.42:1 |
Dimensions
| Overall Length | 2145 mm |
| Overall Width | 820 mm |
| Overall Height | 1245 mm |
| Wheelbase | 1450 mm |
| Ground Clearance | 360 mm |
| Fuel Tank Capacity | 8.0 L |
Chassis
| Frame Type | Steel box-section perimeter frame |
| Caster Angle | 27.0° |
| Trail | 117 mm |
| Front Suspension | Kayaba 41 mm cartridge forks |
| Rear Suspension | Monocross single shock |
| Front Suspension Travel | 300 mm |
| Rear Suspension Travel | 315 mm |
Brakes & Wheels
| Front Tire | 80/100-21 |
| Rear Tire | 100/90-19 |
| Front Brake | Single hydraulic disc |
| Rear Brake | Single hydraulic disc |
125cc Other Specs
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