1989 Yamaha YZ125
Specifications and workshop reference information for the 1989 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 | Liquid-cooled, 2-stroke, single-cylinder |
| Displacement | 124 cc |
| Bore × Stroke | 54.0 × 54.5 mm |
| Compression Ratio | ~8.5:1 |
| Maximum Power | ~34 hp |
| Maximum Torque | N/A |
| Carburetor | Mikuni |
| Lubrication | Premix |
| Fuel Mix Ratio | 32:1 (typical) |
| Ignition | CDI |
| Spark Plug | NGK BR9ES |
| Spark Plug Gap | 0.7 – 0.8 mm |
Transmission
| Transmission Type | 6-speed constant mesh |
| Clutch | Wet multi-plate |
| Primary Reduction | 3.409 |
| Final Reduction | 3.846 (13/50) |
| Overall Reduction | N/A |
Dimensions
| Overall Length | ~2140 mm |
| Overall Width | ~820 mm |
| Overall Height | ~1230 mm |
| Wheelbase | ~1435 mm |
| Ground Clearance | ~355 mm |
| Fuel Tank Capacity | ~8.0 L |
Chassis
| Frame Type | Steel single cradle |
| Caster Angle | ~27° |
| Trail | ~115 mm |
| Front Suspension | Telescopic forks (cartridge type) |
| Rear Suspension | Monoshock (rising rate) |
| Front Suspension Travel | ~300 mm |
| Rear Suspension Travel | ~300 mm |
Brakes & Wheels
| Front Tire | 80/100-21 |
| Rear Tire | 100/90-19 |
| Front Brake | Disc |
| Rear Brake | Disc |
125cc Other Specs
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