O.S. Max-R21 3.5cc nitro on-road engine


O.S. Engine have released photos and specifications about their forthcoming Max-R21 3.5cc nitro on-road engine. Based off of the O.S Speed R2102, we undestand that the Max-R21 would be compatible with R2102’s parts, offrering high performance for a more attractive price.

O.S. Engines


  • Displacement: 3.49cc
  • Bore: 16.08mm
  • Stroke: 17.2mm
  • Power output: 2.75HP/33,000RPM
  • Practical range: 4,000 – 44,000RPM
  • Weight: 350g