The OS FS-90 is a classic, highly regarded 15cc four-stroke glow engine manufactured by O.S. Engines in Japan. Released originally in 1983, it represents the second generation of model four-stroke engines, noted for its unique rear-mounted camshaft design. Because of its build quality, reliability, and smooth operation, it has become a prized piece for vintage radio-controlled (RC) airplane collectors.
Displacement: 15cc (.90 cubic inches).Propeller Selection: Best matched with a 14×6 propeller for ideal load and peak power delivery.
Operating RPM Range: Runs optimally between 8,500 and 9,000 RPM max, with a remarkably low and stable idle down to roughly 1,800 RPM.
Fuel Mixture: Works well with 5% to 15% nitro fuel mixed with castor or synthetic oils. Internal components are automatically lubricated by the fuel mix.
Valve Adjustments: Tappet gaps must only be checked and reset using a feeler gauge when the engine is completely cold.
