Hello All,
I have a new OS .70 FS engine, that i purchased a couple of years back, and did a few flights on my GP Piper Cub.
I used a normal fuel with 20% castor oil and the engine performed very well. After flying i emptied the oil and filled in the after run Oil .

After a year, now when i try to turn the prop i find there is no compression ... It does pull in the fuel, and empties it from the muffler, but there is zero compression ! i checked the plug and it was fine ..

Not sure what i need to do .. i know there is something small or something jammed that may be causing this.

Please provide me with some insights as to how can i fix this ..

THe crankcase breather does give a hissing sound .. so maybe that is taking away the compression, or maybe i need to check the valves ?

Thanks to all
-Gaurav