This document is the owner's instruction manual for the FLAT-TWIN FOUR STROKE ENGINE Gemini Series. It provides detailed information on the controls and other features of the engine. The Gemini Series engine is a scale-type horizontally-opposed twin-cylinder overhead-valve four-stroke-cycle engine, which is an upgraded version of the FT-120 Gemini. O.S. is renowned for its excellence in four-stroke engine manufacturing, and the Gemini Series engines are among their latest products. The O.S. factory has a production history of sixty years and is equipped with fully computerized manufacturing facilities.