OS FS 120 (Pre Surpass) In Box. (CODE H602)

The OS FS-120 Pre-Surpass is a classic, vintage four-stroke RC airplane engine introduced by O.S. Engines in 1983. It represents a significant historical marker for collectors and hobbyists because it was the only four-stroke engine manufactured by OS to feature a split rocker arm design. It was produced for roughly six years before being replaced by the upgraded OS FS-120 Surpass E in 1989.

Design Quirks: Unlike later Surpass models, the rocker arms are buried deeply inside the cylinder head. This internal layout makes accessing and adjusting the valve lash notoriously difficult, as it requires maneuvering feeler gauges within a very cramped space.
Recessed Glow Plug: The glow plug sits deep inside a recessed pocket on the head. The standard recommendation for reliable performance is a high-quality four-stroke plug like the OS Type F.
Carburetor: It utilizes an intake setup and carburetor that closely mirrors the smaller OS FS-90 engine from the same era.