The O.S. SPEED R21 series won the previous World Championships held in the United States.

The "R2105", most of the parts has been newly designed, aiming for consecutive victories at the world championship to be held in Japan this year.

To increase torque on high-grip track surfaces, a newly designed 9-port sleeve is adopted. O.S. SPEED's traditional DLC coated crankshaft delivers linear power from low to top by changing the counter balance. The outer head has been mirror finish and by clear coat from the conventional color to a silver head base has been adopted. By adopting a thrust plate made out of steel, wear due to interference between the connecting rod and the cover plate during rotation is reduced and engine life is improved.

Adopting the latest design to most part of the engine, it is finished with content suitable for the flagship of the O.S. SPEED on-road engine.

Spec
Displacement: 3.49 cc / 0.213cu.in.
Bore: 16.08mm / 0.633 in.
Stroke: 17.20mm / 0.677 in.
Output: 2.80 ps / 2.76 hp / 35,000 r.p.m.
Practical RPM range: 4,000-45,000 r.p.m.
Engine weight: 345.0g / 12.17 oz.
Includes: Reducer(8.5mm RED)/T-RP7 glow plug/Exhaust seal ring(1pc)/ Dust cap set (3mm, 16mm, 18mm 1pc each)