The Thunder Tiger F-91S Four Cycle engine is the latest project from Kaz Mihara, internationally acclaimed engine designer and "father" of the modern 2-cycle engine.
Designed on modern CAD computer equipment and manufactured in Thunder Tiger's state-of-the-art manufacturing facility, the F-91S is certain to establish new benchmarks of value and performance for 4-cycle engines. Featuring CNC machined components, the .91 contains a special gear-driven camshaft and oversize valves for optimum power output. A precision-machined, ground and balanced crankshaft reduces vibration, while a high-silicon content piston and special hardened cylinder provide years of reliable performance. A twin-needle carburetor precisely monitors fuel flow, and the included muffler transforms exhaust noise into a gentle "purr".
