The O.S. ENGINES FS-20 was my first digital restoration of a 4-stroke engine for RC-models. Perhaps because it was the engine with the smallest displacement among my O.S. four-strokes or because I was fascinated by the delicate yet robust construction, it was the first one that I completely disassembled and then modeled in CAD. And compared to the other projects, this one had a relatively large number of components.

But it was worth it! Just because of the cross-section cutaway images or the transparent views that show a lot of the internals and the function. And the rendering images of a fully chromed version. What posters!

About the technology:

The design of the FS-20 was robust and based on the FS-40, which was popular at that time. In the 1980s, the FS-20 was probably the lightest four-stroke engine in series production.

The short stroke layout of the FS-20 ensures a small size and compact dimensions, thus providing easy engine cowling in the model. The needle valve extension is removable. The FS-20 comes with a self-reopening throttle valve, operated by a push button directly in front of the throttle lever. Compared to its size, the engine has above-average power.

Other engines