ORIGINAL: mesaflyer
I pulled the engine (OS 55) out and at first I thought something had happened to it internally, because when I turned the shaft I could feel something rubbing inside. There was not prop on it. So I pulled the back plate off and couldn’t find anything wrong, except that the crank shaft has some in and out play to it. I bolted a prop on, and the rubbing went away, as did the shaft play. Does this sound normal to you guys?
I don't know for sure about the OS .55 but at least for the other 2C O.S. engines I have, there is a small washer behind the prop drive.
This small thin washer "pulls" the crankshaft forward a bit when the prop is screwed in.
With the prop off you feel the in/out play because the washer is not doing it's thing.
DON'T LOOSE IT! And make SURE that it is there.
Without it you WILL feel that "rubbing".
[/quote]