‘The engine is more powerful but at the same time smoother to drive, fuel consumption is improved. What's more, power at low revs is good, but smooth and torquey.’ are the words of 2018-2022 World Champion Davide Ongaro when he talks about the new O.S B21 05 engine.

O.S.SPEED's off-road racing engine has evolved yet again.

The B2105, which has become the fifth generation of the B21 series, is designed to guarantee power that gives an edge in the tough conditions of off-road racing, and to offer a driving feel that consistently demonstrates its performance in any situation.

By redesigning the piston sleeve and crankshaft, the Japanese OS Speed team have created a new, smooth and linear power delivery.

In addition, the effect of a lighter outer cylinder head improves handling in all situations.

Features:

• New cooling head.
• New piston sleeve.
• Backplate with pushplate.
• New balanced DLC-coated crankshaft
• Ceramic rear bearing

Specifications :

• Displacement： 3.49 cc / 0.213cu.in.
• Bore 16.27 mm / 0.641 in.
• Stroke : 16.80mm / 0.661 in.
• Power: 2.68 ps / 2.64 hp at 34,000 rpm.
• Practical RPM range: 4,000-42,000 rpm.
• Engine weight: 348g / 12.28 oz.

Includes:

• P3 glow plug
• Restrictors φ6Ⅱ and φ6.5Ⅱ
• Exhaust gasket
• Set of dust caps engine and carburettor