OS FS-120 4-cycle

[Saxbutt]

I have an older OS 120 4-cycle engine (pre-Surpass) with low hours that I would like to use in a new project. Is anyone familiar with this engine? What type & size airframe would be appropriate? I'm assuming that it won't have the power of a modern 120 4-cycle and have heard rumors that these were somewhat unreliable. Have been unable to run down any specs or info of any kind so far....

[okelly]

Hi Saxbutt,
If I'm not mistaken this is the manual: http://manuals.hobbico.com/osm/fs-120s-e-manual.pdf

Cheers,
Ofir

[Saxbutt]

Wow, Thanks, OKelly- That's my engine! I see this manual is dated 1989. I still have the box mine came in- it included instructions that were typewritten and so must be of earlier manufacture, but I can see this manual pertains to the same engine because of the photos. Some guys thought this engine was a Saito because of the twin valve covers.

[okelly]

Hi Saxbutt,

Sorry to disappoint you, but now that you mention it's the "Saito look-alike" OS, I know what engine you are referring to; It's the 1983 fs120.
Your engine is:
http://www.osengines.com/history/osm640/osm-1983-fs-120.jpg
The one the manual if for ('89 model) :
http://www.osengines.com/history/osm640/osm-1989-fs-120s-e.jpg
I think they share a lot of parts but they are not the same.

Ofir

[Saxbutt]

Guess I should have looked a little more closely- you're right, the '83 model is the one I have. I originally had it in a Giant Super Sporster which it powered adequately at "scale" speeds. I only flew that plane occasionally and so I think this engine has had only a couple of gallons of fuel through it at most. Thanks so much for the pix.

[Saxbutt]

4 Years Later- Needless to say this engine has sat on a shelf in my basement since my last post. However this month I won a raffle at the meeting of our local club (The Grandview Radio Control Sport Flyers)- a Top Flite P-47 ARF (60 size) which will be a candidate for this engine. Am still amassing servos & must complete my current project before beginning this kit.

[fhhuber]

Be sure to us an OS F plug... and I always use 15% nitro heli fuel (extra oil) in my OS 4-strokes.

[Spiritman]

Not too familiar with 4 strokes, but if it is the very early type with exposed rockers, and then it is very definitely no good for stunt. I had one and it just about pulled the skin off a rice pudding! They make beautiful power plants for old timer flying with a little radio assist. They just purr along and make a delightful noise. Wished I hadn't got rid of mine. I used it on new planes before putting in an old sparker, just to get the trim somewhere near. That way I only had one problem at a time.
___________________
cycling (http://www.fitnessqn.com/start-cycling-autumn.html) : The sound of a car door opening in front of you is similar to the sound of a gun being cocked