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O.S. 21XR-B Version II Engine

Check out this redesign of the the 21XR power plant!


21XR-B Version II - Long Stroke

From O.S.

This version of the 21XR-B power plant has been totally re-designed. It's even more reliable, and the new 21J3-I carb is easy to tune. The aluminum cooling head ensures steady power even under harsh conditions. And when you're ready to move up to top competition, you can get up to speed with the 21XR-B Version II. This engine is upgradeable with high-performance O.S. Speed Parts, letting you realize your full winning potential. Equip your ride with the 21XR-B Version II, and start owning the podium.

Engineered for up-and-coming 1/8 scale buggy club racers, with upgrade capability for competing at the highest levels. A dependable, low-maintenance engine that fits into most any modeler's budget.

The 21J3-I carb comes with two intake restrictors that can be swapped out quickly and easily for fine-tuning to meet track conditions. The yellow (7mm) restrictor (pictured) gives you more bottom end, while the red (8mm) restrictor delivers more top end. close-up of cylinder head The blue-anodized aluminum cylinder head delivers superior cooling.


  • Stock Number: OSMG2056
  • Displacement: 0.211 cu in (3.46 cc)
  • Bore: .641 in (16.27 mm)
  • Stroke: .661 in (16.8 mm)
  • Practical RPM: 4,000-40,000
  • Power Output @ 33,000 rpm: 2.45 ps/2.42 hp
  • Weight: 13.40 oz (380 g)
  • Includes: P3 turbo plug

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