OS SPEED R21 GT is an all-new 5-port engine.
It features a newly developed piston and 5-port cylinder, crankshaft, crankcase, Specially made to fit on-road GT track. 
The OS SPEED R21 GT has a 7mm carburetor restrictor.

Tech specifications:

• Displacement: 3.49 cc
• Bore: 16.08mm
• Stroke: 17.20mm
• Intake ports: 5-port
• Exhaust port: 3-port
• Practical RPM range: 4,000 – 42,000 rpm
• Max. power output: 2.65 ps / 2.61 hp / 34,000 rpm
• Weight: 369Gr.

With tuned pipe T2060SC and 70mm manifold