The new O.S.SPEED R21 GT engine has been introduced to compete in the 1/8th scale GT touring category – with O.S. clearly looking at the IFMAR World Championship.

Performance has been improved over the entire range compared to its predecessor, the 21XZ-GT. The crankcase is a refinement of the R2101, which has an excellent battle history in on-road racing. The cylinder/piston uses 5 scavenged ports plus 3 exhaust ports that have cleared IFMAR regulations. The new crankshaft design has an emphasis on pick-up by press-fitting the DLC coating and counterweight that inherits the OS Speed tradition. Considering the GT touring racing scene, O.S. have adopted a new outer head that improves cooling performance. The engine is fitted with a new design 22E (B) GT carburettor that is a double adjustment type that emphasises pickup performance that smoothly follows the rise from each corner, which is important in GT touring. The reducer meets IFMAR regulations.

Specifications
Weight	369g (13.02oz)
Displacement	3.49cc (0.213 cu.in.)
Bore	16.08mm (0.633″)
Stroke	17.20mm (0.677″)
Power Output	2.65ps (2.61hp) @ 34,000 rpm
Practical RPM	4,000 – 42,000 rpm

Spec

• Brand: OS Engines
• Part No: L-OS1CC00
• Displacement: 3.5cc (0.21ci)
• Starter: Flywheel Start