The 125cc Junior MAX engine is used for MAX Challenge racing for drivers aged 13-16 years old. This is the youngest group that is eligable for the Rotax MAX Challenge Grand Finals.
Technical Specifications
| Age | 13-16 years |
| Race Class | National – International |
| Horsepower | 20.4 hp (15 kW) at 8,500 rpm |
| Maximum Torque | 12.5 ft./lb. (17 Nm) at 8,500 rpm |
| Weight | Bare engine: 26.0 lbs (11.8 kg), with complete power pack: 52.0 lbs (23.6 kg) |
| Special features | Junior cylinder without exhaust valve |
| Power Pack | Silencer, carburetor, fuel pump, engine, exhaust system, radiator, battery, battery box, cable harness, start button, ON/OFF switch |
| Chassis compatibility | wheel base from 780 mm to 1,050 mm |