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SKU: OSM11685

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Product Information

This is the O.S. Engines 12XZ Speed Spec III .12 Nitro Touring Car Engine. O.S. Engineers have taken superior Speed Spec performance to the next level. In addition to smoother acceleration from idle to full throttle, the 12XZ Speed Spec III also has increased low-to mid-range torque. Drivers will still enjoy the same impressive top end speeds that 12XZ Speed Spec engines are known for — with the bonus of improved fuel mileage. In fact, acclaimed on-road champion racer Takaaki Shimo utilized all of the 12XZ Speed Spec III’s advantages to claim victory in the 2012 Japan Nationals.

In-Depth Features:

  • Cooling Head: The outer head is 1mm shorter and sits 6mm lower over the crankcase. This decreases the engine's overall weight while also lowering the CG and aiding in cooling. 
  • Carburetor: The redesigned 12F2(B) carburetor delivers sharp acceleration and instant throttle response. It also allows for easier, more reliable tuning. 
  • Crankshaft: This crankshaft features DLC coating, pressed-in Tungsten weights and ceramic rear ball bearing. 
  • Cylinder/Piston: The cylinders liner's outer diameter is slightly thicker (0.5mm), with redesigned ports for better air/fuel flow that boosts mid-speed torque and extends fuel mileage. The piston features a tapered surface with a depression that works with the button to maximize combustion and power. 


  • Redesigned head button for better performance and improved acceleration
  • Updated cylinder liner and piston improve mid speed torque and fuel mileage
  • The slide valve's shape allows for a smoother flow of fuel and air

0.128 cu in (2.1cc) 
Bore: 0.543in (13.8mm) 
Stroke: 0.55in (14.0mm) 
Practical RPM Range: 5,000-44,000 
Output: 1.73hp @ 35,000 RPM 
Weight: 7.9oz (225g) 


  • 12XZ Speed Spec III Engine
  • 12F2(B) carburetor
  • RP6 glow plug
  • Exhaust seal ring
  • Dust cap set
  • 5.5mm red carburetor reducer (venturi) 

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