Rotax 125 Max Junior Evo

The Rotax 125 Junior Max EVO is the latest model in a long line since Rotax manufactured its very first kart engine more than 40 years ago.

Rotax has always focused fully on delivering an exciting and affordable driving experience combined with excellent reliability.

Rotax is actually the only manufacturer in the world offering a factory warranty on their racing engines – proof of the high quality these hand-built engines from Austria deliver.

Technology:

With the Rotax 125 Junior Max EVO, you get everything you could ask for from a modern kart engine:

• Reliable electric start with long battery life
• Official apps that help you perfectly fine-tune your engine
• Engine management (ignition and more) is fully controlled by the engine ECU (Electronic Control Unit), ensuring perfect results every time
• All components are manufactured in-house at Rotax’s state-of-the-art factory in Austria
• The engines offer very long service intervals – up to 50 hours of operation, which is significantly longer than all comparable competitors

Engine Components:

Crankcase: The crankcase is manufactured from injection-molded aluminum.

Molten aluminum is injected into a mold under pressure exceeding 15 bar. The high pressure guarantees a strong and solid casting with perfect results.

After casting, the crankcase is machined by computer-controlled milling machines with extremely high precision. The entire crankcase is then powder-coated with a durable surface finish.

Piston and Cylinder: The cylinders are also cast in aluminum before being CNC-machined to achieve the smoothest and most precise result possible.

The cylinder bore is Nikasil-coated. Nikasil is one of the hardest surface treatments available and offers near-unlimited durability.

Another major advantage of Nikasil is that only a 2% oil mixture is required, which is better for both the environment and your wallet.

The piston is manufactured from forged aluminum and coated with a Teflon surface after machining. This increases durability and provides the best possible performance through reduced friction.

Cooling: All Rotax engines feature a closed water-cooling system that operates without external water pumps. The high flow rate and large aluminum radiator ensure the correct operating temperature (50–60°C) even during demanding driving conditions.

Ignition: The ignition system is digital and fully electronically controlled by the engine’s ECU. With the help of a sensor located at the crankshaft, you are guaranteed precise ignition timing every time. You also benefit from a variable ignition curve that automatically adapts to engine RPM for maximum performance.

Clutch: The clutch, manufactured from hardened steel, transfers engine power to the drive chain and then to the rear axle.

The clutch is normally maintenance-free and lasts for several years. The engine sprocket is mounted inside the clutch drum, allowing you to quickly change gearing in less than a minute.

Carburetor & Fuel: A powerful vacuum-operated fuel pump delivers fuel to a 34 mm Dellorto carburetor specially developed for the Rotax engine.

The carburetor can be adjusted by changing jets and adjusting the throttle needle. Information about recommended jetting is provided through the Rotax App, which uses your location to calculate the optimal setup based on temperature and air pressure.

Mounted on the carburetor is the engine air intake. Air is routed through a foam filter into the carburetor, ensuring clean airflow with the correct volume.

Thanks to the smart design of the airbox, the engine performs reliably even in heavy rain conditions.

Specifications:

• Displacement: 125cc
• Power Output: 23 hp at 8,500 rpm
• Torque: 19 Nm at 8,500 rpm
• Weight: 11.8 kg (Engine only) / 23 kg (Complete engine package)
• Ignition: Electronic ignition
• Electrical System: 12V 7Ah
• Cooling: Water-cooled

You receive everything needed to run and operate your Rotax engine. Included in the engine package:

• Complete engine
• Radiator and cooling hoses
• Exhaust pipe, silencer, and exhaust mounts
• Fuel pump, carburetor, and fuel filter
• Throttle cable
• Intake silencer / airbox with mounting bracket
• Complete electrical system (spark plug, ignition coil, wiring harness, starter motor, battery, control panel, ignition sensor)
• Frame mount for battery and electrical system
• Instruction manual and engine logbook