The O.S. Max 90 FSR is a legendary, vintage 14.89cc (0.908 cu in) two-stroke R/C aircraft engine introduced in 1978, highly regarded for its power, reliability, and robust construction. Known for its performance in pattern aerobatics (F3A).
Displacement: 14.886 cc (0.908 cu in)
Bore: 27 mm (1.063 in)
Stroke: 26 mm (1.024 in)
Power: 2.28 bhp @ 13,100 RPM (ABC version)
Weight: 676 g (23.8 oz)
Induction: Front rotary valve Carburetor: Typically 7D
Design: Originally introduced as a ringed engine in 1978, it was updated to an ABC (Aluminum piston, Brass liner, Chrome plating) set in 1979, which increased power by 5%.Reliability:
The 90 FSR is often described as one of the best engines ever produced by O.S.
.Application: It was designed to pull large props without requiring a tuned pipe, making it popular for large aerobatic planes.
Variants: While not officially produced as a marine engine, its design served as the basis for the rear-induction O.S. 90 RSR-M marine engine.
