IAME Reedster V – OKJ – 125cc

The new IAME Reedster V OKJ is the power unit developed for the CIK-FIA OK Junior class and is the natural evolution of the World Championship winning Reedster IV. The project integrates race-proven solutions such as the low-mounted front balance shaft to lower the centre of gravity, the extremely lightweight elliptical connecting rod reducing internal turbulence, and the water-cooled crankcase which minimizes intake air temperature. The result is a stable, consistent and highly competitive engine for top-level Junior racing.

🔵 Class: CIK-FIA OKJ
🔵 Configuration: Single-cylinder 2-stroke
🔵 Displacement: 124.08 cc
🔵 Bore: 53.89 mm (max 54.08 mm)
🔵 Stroke: 54.40 mm
🔵 Intake system: Reed valve
🔵 Lubrication: Oil mixture
🔵 Cooling: Water
🔵 Transmission: Direct drive
🔵 Starting system: Push-start
🔵 Digital ignition with rev limiter: 14,000 rpm
🔵 Balancer shaft: present

The cylinder is made from high-strength sand-cast aluminium and redesigned to optimise coolant circulation through CFD analysis, ensuring uniform temperatures. The cast-iron liner is machined on 5-axis CNC equipment with extremely tight tolerances for consistent performance across the production. The two-piece cylinder head is CNC-machined, allows flexible combustion chamber architecture, and includes an integrated decompression valve.

The direct-drive transmission is positioned very close to the crankshaft axis, reducing bending and mechanical stress. The crankcase incorporates a new airflow concept that increases cooling efficiency in the critical area between the engine and its mount. The forged steel CNC connecting rod with “knife-shape” profile is combined with precision roller bearings. SKF-engineered main bearings maximise crankshaft alignment accuracy and reduce friction. The PVL digital ignition uses a low-inertia internal rotor and includes the OKJ-specific 14,000 rpm limiter. The exhaust system is a one-piece FIA-homologated OKJ design.

🔵 Two-piece cylinder head with decompression valve
🔵 Precision roller main bearings
🔵 Complete balance shaft
🔵 CNC-machined reed valve duct with removable inlet spacer
🔵 Separate reed block carrier
🔵 FIA-homologated digital ignition with 14,000 rpm limiter
🔵 H.T. coil/electronic box on vibration dampers
🔵 NGK BR10EG spark plug with cap
🔵 CNC-machined exhaust manifold
🔵 Homologated OKJ exhaust with silencer
🔵 Z12 splined sprocket

🔵 Carburettor not included
🔵 Engine mount plate not included
🔵 Intake filter not included
🔵 Cooling system not included