OS engine FS series Surpass 91 four stroke

Description

This is one of my collections. It  is rare and unique design, there is the drain plug at the bottom of the crankcase, and the breath fitting on the rear cover. This fitting is at the center, therefore the lubricant could stay in the bottom half of the crankcase to lubricate all components inside the engine. OS stopped this design, I believe for the marketing reason. It would last too long. I kept in the glass case after two seasons, may be ten flights.
I filled the crankcase with a thin lubricant as it was new. At the end of the flying season, I
remove the drain plug,
connect a hose to the breather, and dip other end in a small can of the lubricant , then crank the engine to clean the inside and fill with the new lubricant for the storage.
It was on my Piper Cub for two seasons, and then, It stayed in the glass case at least two decades in my hobby
collection
room.
I am in the process of moving to a much smaller home. Before listing for sale, I ran a test with 10% nitro gas and 15x8 prop that I have.
-Peak RPM is 8,700.
-Smooth idle at 1800 RPM
-Valve gap :.0025 on both valves
You can download the manual from the internet.
This engine would rev up to 11,000 RPM with the smaller prop.
The prop jam nut has the extension for the centered hole spinner.
The prop size will depend upon your plane, and the way you want to fly.
THIS ENGINE IS READY FOR THE INSTALLATION. YOU MAY OR MAY NOT HAVE TO ADJUST THE HIGH SPEED NEEDLE VALVE DEPENDING UPON THE ELEVATION OF YOUR AREA.
Please email for any question.
THANK YOU FOR LOOKING