OS Speed B2105 Off‑Road Nitro Engine

The OS Engines OS Speed B2105 is the fifth generation of the acclaimed B21 off-road racing series, engineered to deliver confident power and exceptional drivability across changing track conditions. With a redesigned cylinder liner and crankshaft, this B2105 provides smooth, linear power delivery that supports precise throttle control from low to high rpm.

A lighter outer head contributes to improved handling characteristics, helping the engine respond consistently in demanding off-road situations. The 3.49 cc displacement pairs with an output of 2.68 ps (2.64 hp) at 34,000 rpm, while the practical operating range of 4,000–42,000 rpm offers a wide, usable band for racing setups. Weighing 348 g, the B2105 balances performance with a compact, race-ready form factor. Part number SCH-OS1EK00.

Technical Specifications

• Displacement: 3.49 cc (0.213 cu. in.)
• Bore: 16.27 mm (0.641 in.)
• Stroke: 16.80 mm (0.661 in.)
• Output: 2.68 ps (2.64 hp) at 34,000 rpm
• Practical rpm range: 4,000–42,000 rpm
• Engine weight: 348 g (12.28 oz)

Standard Accessories

• Glow plug T-P3
• Reducer φ6 II
• Reducer φ6.5 II
• Exhaust seal ring
• Dust cap set 12-30 (φ3, φ16, φ18)

Designed to secure strong, controllable power in harsh off-road racing environments, the OS Speed B2105 focuses on a steady, confidence-inspiring driving feel that helps extract performance in any situation.