ghost123uk

Hi all

This recent talk of OS engines has lead me to try and clarify in my head the differences between the OS engine suffixes.

I own an OS 35FP ( in a stunter ) this engine is, I believe, made in the 1990's and is the all silver type.

I believe there is an OS 35FS also.

What are the differences ?

Also the later blue coloured ones come with various suffixes, is there a general rule one can follow to I.D. the spec of these ( such as all FS are ballraced or ABC etc etc ) ?

John in the N.W. UK

CLpilot

My Feedback: (1)

I am pretty sure that the FS you see listed means Four Stroke. I don't have any experience using a four stroke on a stunt planes, but I seen it done. Mostly with the bigger engines. They are a lot heavier and not as powerful for their size.
Got to love those FP engines. I have 3 and they all run great. Too bad O.S. decided to make cheaper engines instead of keeping a better engine on the market.

Jay

Phlip

I would agree that the FS means four stroke. The blue ones are the LA series, and they're pretty good engines (great for the price) too. The LAs make good C/L engines, I hear.

downunder

The only way to try to make any sense of OS designations is to got to the timeline at http://www.osengines.com/history/ostimeline01.html and work your way through. This isn't an official OS site because it's done by the American importers and there are a few inaccuracies and isn't totally complete but it's by far the best around.

If you follow it through you'll see the 35FP was first made in 1984 but you'll see it listed again in 1998 when they changed it to a remote needle valve so it had quite a long run. Strangely enough this is where one of the errors is because the '98 photo is supposed to be the CL version (FP-S) but it's got the RC carb. I can't find any 35FS though.

As far as the suffixes go, if it says 40 LA then it's the standard RC version. If it says 40 LA-S then it's CL, -M for marine, -H for helicopter. There are a couple of weird suffixes though like -B so it's up to your imagination as to what they meant by it

Ployd

I beg to differ on the identification of the OS 35FS as a 4stroke designation as there was an FSR (4stroke-racing ) handle applied to some of the 2stroke engines in the late 70's (these were twin ballrace) and while I do not have my file handy, believe the FS is the plain bearing version.

Ployd

ghost123uk

Yes Ployd, this is what I thought from mutterings I have heard at the flying field.

I have given up trawling the web for definate answers as I have work to do !!

gcb

What the designations mean depends on what year you are looking. At one point FS meant front induction, schnuerle porting. The FP meant front induction, plain bearing. The FP-S was front induction, plain bearing, stunt (CL). At other times, it means something else. []

George