What is this engine used for? (O.S.MAX 91F SR) Looks like an older OS engine, but since I am fairly new to sport, I do not know what this could be used for. Any information is appreciated.

Thanks,
EKF

This is going to sound silly but are you sure it's not a Thunder Tiger F91S? That's a four stroke they do. http://www.thundertiger4u.com/thunde...s-p-13121.html

I believe it was a knock-off of an old OS engine so maybe you have the original.

The only OS FSR engines I'm aware of were the .10 FSR, .25 FSR, .40FSR, .50 FSR, .61 FSR and 1.08 FSR. If it's an older engine, are you sure it's not a .91 FS Surpass?? The FSR models were 2 strokes, and until recently, the only .91 airplane engine OS made was a 4 stroke. There is a current .91 2 stroke, but it's an FX. It could also be (depending on its age) just a regular .91 FS. Can you post a pic or 2?

I have tried to upload a picture. The engine is for sale on Ebay. I was just curious as to which engine it actuall was.

Here is description if picture did not make it.

"This is a 1970's (?) O.S. MAX 91F SR model 19010 that was purchased at GRANTS for $$224.99."

Here's the 2007 equivilent. http://www3.towerhobbies.com/cgi-bin...&I=LXBY47&P=ML
You can probably find one of these on E-Bay too! YEP!

http://cgi.ebay.com/OS-MAX-O-S-91-FX...QQcmdZViewItem

Yup. It's old enough not to be listed on OS' website. What is it used for? Well, any .60 - 1.20 size 3D, sport or scale plane. Looks like a nice engine. Good luck finding parts for it though. I would imagine the piston and sleeve, connecting rod, bearrings and crankshaft are quite different from the FX version sold today. If it's brand new, and broken correctly, you may never have to replace any parts. It's probably a bit heavier than the ones sold now, but it should put out close to what the new ones do (between 2.5 and 2.8 BHP). Keep in mind though, a brand new one only costs $210 with warrantee.

http://www.osengines.com/history/ostimeline11.html

There was also a 90FSR made in 1978. That timeline web site is very handy for tracking down OS engines but it isn't totally complete, maybe 99% so near enough .

The 91FSR is a fine engine for a scale model, not so great for sport/pattern or current 3D type flying- too big physically and too heavy.

Where the current 91FX is relatively light and compact based on the 61FX case, the 91FSR was heavy duty and based on a larger, heavier case than the 61FSR of the same timeframe.

The 91FSR was later increased in displacement to become the 1.08 which basically made the 91 obsolete. The 91 & 1.08 FSR's were intended for the exploding giant scale scene in the late 80's...torquey, reliable engines that would turn a big prop and fly some fairly good size models. In those days there were not all that many options for an engine this size. Saito, OS & Enya all had 1.20 four strokes out but these early models were none too powerful. Gas engines from Quadra and Zenoah were around but for bigger models altogether.