I guess this is posted twice.. I think a thrown crankshaft rod...
If you can take out the plug on most engines the piston top can be seen throught the plug hole. See it the piston is moving when the engine is slowly turned by the blade or pull rope.
moving = Good
not moving = Bad
Drain the oil see if there is any shiny chunks in the oil...
What type/ brand of engine is it?
Good luck,
Friiy