IAME Screamer IV – KZ/KZ2 Engine

The IAME Screamer IV is the latest evolution for the KZ and KZ2 gearbox categories. CIK-FIA homologated, it benefits from experience gained with the Screamer III and introduces a newly designed crankcase that is lighter and more compact. A redesigned cylinder and optimized component layout deliver top-level consistency, fast throttle response and excellent thermal efficiency.

🔧 Engine type: single-cylinder 2-stroke
🔧 Displacement: 124.59 cc
🔧 Bore: Ø 54.00 mm (max Ø 54.08 mm)
🔧 Stroke: 54.40 mm
🔧 Inlet system: reed valve
🔧 Ignition: analog, CIK-FIA
🔧 Transmission: 6-speed
🔧 Cooling: water
🔧 Starter: push start
🔧 Carburettor: Dell’Orto VHSH 30

🟦 Cylinder
High-strength aluminium sand-cast cylinder. CFD-optimized water jacket for efficient cooling and reduced wall thickness. Ni-Si coated liner ensures durability and production consistency.

🟦 Two-piece cylinder head
CNC-machined extruded aluminium. Allows unrestricted adjustment of squish and cylinder positioning. Integrated water jacket for uniform cooling.

🟦 Crankshaft
Composite type with 20 mm crankpin and 25 mm main bearings. Balanced with metallic inserts. Made from forged, case-hardened and ground steel.

🟦 Connecting rod
CNC-machined forged steel with reinforced knife-style design. Precision roller cages on both ends.

🟦 Main bearings
Special roller bearings co-developed with SKF to improve crankshaft alignment and reduce friction. Press-fit inner ring protects the crankshaft journals.

🟦 Piston
High-silicon alloy 2-stroke piston with a single flat chromium-plated ring.

🟦 Crankcase & primary cover
High-resistance sand-cast crankcase. Airflow-optimized for improved cooling around the engine mount. Revised “desmo” cam and preselector location for a faster and more direct gear shift.

🟦 Transmission
6-speed gearbox with 5-disc dry clutch. Dedicated lubrication for primary shaft. Free gears on needle bearings to minimize friction. Chain line positioned close to engine center to reduce shaft flex.

🟦 Exhaust
13-sector CIK-FIA homologated exhaust, specific for KZ/KZ2.