OS Max-B21 Combo Set

The OS Engines MAX-B21 Combo Set (SCH-OS1EG01) is a versatile 1/8-scale nitro package that includes a matched pipe. Designed for users from entry-level through to sports racers, it delivers smooth, controllable power and excellent value, drawing on O.S. Speed series heritage for dependable performance in both on- and off-road racing.

Its outer head, derived from the MAX-21XR-B Ver.3, has been lightened to enhance response, while a revised inner head combustion chamber improves efficiency and throttle pickup in the low-speed range. The result is more stable idling, reduced tendency to stall, and easier carburettor tuning at the track.

Key Features

• Balanced speed and power delivery for racing use
• Reduced-weight outer head based on MAX-21XR-B Ver.3
• Revised combustion chamber for improved efficiency and low-speed response
• Stable idle to help avoid stalling; easier carburettor adjustment
• Combo includes pipe for a complete engine-and-pipe package

What’s Included

• P3 glow plug
• Reducer 6 mm (Orange) and 7 mm (Yellow)
• Exhaust seal ring
• Dust cap set: 3 mm / 16 mm / 18 mm
• Pipe (included as part of the combo)

Specifications

• Displacement: 3.49 cc (0.213 cu.in.)
• Bore: 16.27 mm (0.641 in.)
• Stroke: 16.80 mm (0.661 in.)
• Output: 2.6 ps / 2.56 hp @ 34,000 rpm
• Practical RPM Range: 4,000–41,000 rpm
• Engine Weight: 361 g (12.73 oz)
• Part Number: SCH-OS1EG01

Suggested Compatibility

• 1/8 nitro off-road
• 1/8 GT