This is the OS Engines 81FS-a four stroke ring engine, with 60RA carburetor and included OS F5030 muffler.  Packing more power into 60-size planes!

Features:

• Mounts easily in the same space as the FS-70SII with no modifications.
• A rubber O-ring on the muffler's multi-positional manifold helps prevent oil leakage.
• The specially designed lubrication system eliminates the need for crankcase ventilation.
• The 60RA carburetor is equipped with a venturi that reduces the chance of fuel leaking out onto the cowl, while also creating more positive air/fuel flow.

Specifications:

• Displacement: 0.809 cu in (13.26 cc)
• Bore: 1.091 in (27.7 mm)
• Stroke: 0.866 in (22.0 mm)
• Weight w/muffler: 19.63 oz (556 g)
• Practical rpm range: 2,200-12,000
• Output: 1.3 hp @ 11,000 rpm