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

O.S. Engine #13875 - 21XZ-R Ver.II On-Road Engine
Price:
AUD$502.54
Brand:
O.S. Engine
Model:
OS-13875
Please kindly input your name and email address, we will inform you once we have the restocking.
Or you may find similar product under the
category
Write a review

Compact Race Power from the O.S. Engine 21XZ-R Ver.II

The O.S. Engine 21XZ-R Ver.II, model OS-13875, is a compact, high revving unit intended for serious on-road performance. It combines a small package with a flexible powerband suited to sprint and endurance formats.

Dimensions and Rev Characteristics

At 3.49cc displacement the engine uses a 16.27mm bore and 16.8mm stroke to produce a usable RPM spread of 4,000 to 45,000. This allows fine tuning of gear ratios and throttle response for different race styles.

Performance Numbers

Output is listed at 2.75ps at 33,000rpm, equal to 2.79hp, while overall mass is 343g. These figures give tuners a strong base to balance speed and handling on tuned chassis.

Built for Tuners and Racers

Intended for pilots who do setup work, the 21XZ-R Ver.II responds well to needle adjustments and exhaust selection. It is a practical choice for racers who prioritise on-track consistency.

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 is a solid choice for racers who need a nimble, tuneable engine for competitive on-road use.

What exhaust layout works best with this engine?

A tuned on-road header and pipe that complements the engine's high rev nature will help extract top end. Match the pipe length and backpressure to your chassis and gearing for best results.

How sensitive is the 21XZ-R Ver.II to fuel quality?

This engine performs best on clean, high quality nitro fuel. Impurities can affect needle valve behaviour and overall reliability, so use filtered fuel and a good tank setup.

Can I use this engine in endurance events?

Yes. With correct jetting, cooling and planned pit service, the 21XZ-R Ver.II can be managed for longer runs. Focus on stable settings and routine inspections between stints.

What tuning changes help low speed driveability?

Richer midrange and slightly larger main jet steps can improve low speed tractability. Make incremental changes and test on track to retain smooth acceleration out of corners.

Copyright © 2008-2026 rcjaz.com.au All rights reserved