The latest revisions to the new RM125 include; Smaller diameter piston ring locating pin to improve ring sealing and increase power output. The reed valve intake area and exhaust pipe have been reshaped. Crankshaft balance has been revised to offer even smoother torque delivery at low RPM Renthal-made aluminium tapered bars, reducing vibration and weight are now included at standard.
| Overall length: | 2145mm (84.4in) |
| Overall width: | 830mm (32.7in) |
| Overall height: | 1275mm (50.2in) |
| Wheelbase: | 1450mm (57.1in) |
| Seat height: | 950mm (37.4in) |
| Dry Mass: | 87kg (191.8lbs) |
| Fuel capacity: | 8.0litres (1.8gallons) |
| Engine capacity: | 124cc |
| Engine: | 2-stroke, liquid cooled |
| Bore: | 54 mm x 54.5 mm |
| Compression ratio: | 8.3/9.9 : 1 (Ex. valve open/Ex. valve close) |
| Lubrication: | Fuel/oil mixture of 30 : 1 |
| Ignition: | Digital CDI |
| Fuel system: | MIKUNI TMX38SS single |
| Transmission: | 6-speed constant mesh |
| Drive: | Chain |
| Front suspension: | Showa telescopic forks, pnuematic / coil spring, oil damped |
| Rear suspension: | Swingarm, link type, SHOWA piggyback-resevoir shock |
| Front brakes: | Disc |
| Rear brakes: | Disc |
| Front tyres: | 80/100-21 51M |
| Rear tyres: | 100/90-19 57M |