O.S. Engine OS-13875 21XZ-R Ver.II Competition Engine  [OS-13875]

O.S. Engine #13875 - 21XZ-R Ver.II On-Road Engine
Price:
£269.69
Brand:
O.S. Engine
Model:
OS-13875
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Precision On-Road Performance from the O.S. Engine 21XZ-R Ver.II

The O.S. Engine 21XZ-R Ver.II, model OS-13875, targets competitive on-road use where high RPM capability and precise response matter. It is engineered to deliver consistent performance lap after lap.

Internal Design and Rev Window

Featuring a 3.49cc displacement with a 16.27mm bore and 16.8mm stroke, the engine operates effectively across a practical RPM range of 4,000 to 45,000. This makes it adaptable to different gearing and track demands.

Output Figures and Mass

The unit produces 2.75ps at 33,000rpm, equivalent to 2.79hp, and weighs 343g. That output combined with the light mass helps maintain nimble handling while providing competitive power.

For Experienced Tuners

Best suited to experienced hobbyists, the 21XZ-R Ver.II benefits from careful jetting and break-in. It responds well to setup changes and supports fine tuning for lap time gains.

Specifications

  • Displacement: 3.49cc (0.213cu.in.)
  • Bore: 16.27mm (0.6405in.)
  • Stroke: 16.8mm (0.661in.)
  • Practical RPM: 4,000 ~ 45,000
  • Output: 2.75ps/33,000rpm (2.79hp/33,000rpm)
  • Weight: 343g (12.08oz.)

The O.S. Engine 21XZ-R Ver.II suits tuners seeking a lightweight, high revving motor for competitive on-road racing applications.

What electronics should I pair with the 21XZ-R Ver.II?

Use a reliable glow driver and a fuel system with good filtration. Ensure your throttle servo and linkage are precise to make the most of the engine's responsive throttle curve.

How often should I check the needle settings?

Check idle and main needle positions before each meeting and after any changes to gearing or pipe. Small shifts in conditions can require tiny readjustments for optimal performance.

Is any special preparation needed for race day?

Prepare fresh fuel, confirm carburettor and exhaust fittings are secure, and warm the engine gently during practice laps. A consistent setup routine reduces variables on race day.

Can this engine be used in vintage or scaled models?

While optimised for on-road competition, the 21XZ-R Ver.II can be installed in scaled models where its size and mounting arrangements are compatible, but expect to tune for different drivetrains and bodywork.

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