Hi,

I have an OS 91 4 stroke that came with a plane I bought from someone. I need to get a couple of parts for the engine but I am not sure if there are multiple versions of this engine out there and if so which one I have. I looked at the OS site and they show a "surpass" and a "surpass with pump". Mine is just a baisic 4 stroke so I am sure it is not the "pump" model.

Can I assume that the pasts from the other 91 will fit ? I need a rocker cover and a "back plate". I had an abrupt "landing" that cause some issues................=o)

any help will be appreciated.

jon

Are the pushrods in front or behind the cylinder?

You can never make assumptions about engine parts, Minn Flyers question above is a key question. Unless the Pushrods are in front then nothing will be interchangable and parts are not readially avalable.

If you have no info on the engine try to post a picture.

the 91 surpass and surpass ll both have the pushrods in front the fs-90 had them in back.if the valve cover is black it is a surpass ll .most of the common parts will interchange between both engines.the pump engines use most of the same parts except the back plate and carb.if you check on the parts desciption it will list both engines if it fits.

you can check part numbers here
http://www.osengines.com/parts/
the backplates and rocker covers for both series of engines are different so you will need to know which you have

Hi,

I added a picture.

jon

I'm so glad you said that, I was wondering if the other guys were the ones going in for eye surgery!!!!