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INNengine 1S-125.
Pre-order now


Due today. Fully refundable.
Estimated delivery date: December 2023

No longer available for pre-ordering


Light, compact and uniquely powerful, we employed aerospace industry design standards and software to develop the REX-B: INNengine´s bid for drones and RC aviation purposes… and it’s a ton of fun to fly.

The first of its kind, the 4 cylinder proprietary INNengine technology keeps all moving parts in perfect equilibrium at all times suppressing vibration completely. Having two combustion events per rev means power is delivered with the same periodicity of a V8 engine reducing power spikes and increasing smooth performance.

And on the subject of power, the REX-B 125cc produces a max power output of 22.7HP at just 6000rpm! Generating an astounding cc/hp power ratio of almost 5 thanks to its 1Stroke technology.


  • Ultra-compact platform at just 214mm in length and 146mm diameter.
  • Aerospace grade aluminum construction bringing weight down while offering extreme toughness and durability.
  • 4 cylinder camtrack configuration with simple harmonic cinematic: suppresses both primary and secondary imbalances. No need to compensate.
  • INNengine’s patented 1Stroke technology: offering twice the power delivery of a 2Stroke with the same power periodicity delivery of a V8 engine.
  • Enhanced Equal Engine air cooling system: having all 4 cylinders axially oriented against the airflow means equal cooling throughout the platform and of each cylinder as well as optimum refrigeration with the hotter areas exposed directly against the wind flow ensuring reliable functioning under the most demanding situations.


  • ENGINE BLOCK: aerospace grade aluminum 7075-T6 precision CNC machined and treated by hard anodizing. Top quality hardened steel guide rods, rectified & super finished.
  • CAMTRACK: proprietary hardened and spring temper steel treatment, 9 axis precision CNC machining for 3D curvature camtrack: suppressing over accelerations. Low temp nitruration post treatment & super finishing.
  • 1S 4R-AXIAL® CYLINDER: aerospace aluminum 6082-T6 for max quality. Nikasil treatment and burnish post treatment for improved surface strength.
  • PISTON BODY: aerospace grade aluminum 7075-T6 precision CNC machined and treated with an 80-micron hard anodizing layer.
  • PISTON HEAD: aerospace aluminum 6082-T6 fully precision CNC machined (no casting for max quality) with the new coupling system allowing for improved truncated cone piston shape.


*Discount applied to the first 200 reservations on the final price.



125.7 cc

Power output

22.7HP@ 6000rpm


L:214mm x ⌀146mm



Cylinder bore/Stroke

⌀40mm / 25mm

Speed range

600 – 6000 rpm

Cylinder arrangement

1S 4R-Axial® INNengine patented technology



Lubrication ratio


Compression ratio


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