OS Speed R21GT II

The OS Engines O.S. Speed R21GT II (part no. SCH-OS1DT00) advances the highly regarded R21GT platform with targeted refinements for GT on-road racing. It preserves the smooth running and strong fuel efficiency of the previous model while delivering a more emphatic power feel in the mid and low ranges thanks to a revised crankshaft counterbalance. A newly designed inner head enhances idling stability, and the addition of an inner head O‑ring helps cut vibration and improve dust resistance. The outer head has also been trimmed for reduced weight, rounding out a focused evolution for competitive GT drivers.

Key Features

• Retains the smooth feel and good fuel efficiency of the original R21GT
• Revised crankshaft counterbalance boosts medium and low speed power
• New inner head design improves idling performance
• Inner head O-ring reduces vibration and enhances dust resistance
• Lightened outer head for an optimised overall package

OS Engines also offers a combo set featuring the TB01 (EFRA2042) tuned silencer and MB01-70 manifold, providing an integrated exhaust option.

Specifications

• Displacement: 3.49 cc (0.213 cu.in.)
• Bore: 16.08 mm (0.633 in)
• Stroke: 17.20 mm (0.677 in)
• Output: 2.65 ps (2.61 hp) @ 34,000 rpm
• Practical rpm range: 4,000–42,000 rpm
• Weight: 362 g (12.77 oz)

Standard Accessories

• Glow Plug RP7
• Venturi 7.0 mm (RED) AL2
• Venturi 7.0 mm (RED) AL2
• Exhaust seal ring
• Dust cap set (φ3, φ16, φ18)