Small Engines (Lawn Mowers, etc.): Engine clicks really loud, visible problem, tall grass

Question
I have a 7.0 Craftsman 22 inch push mower and I was mowing tall grass when all of a sudden it started to click really loud.  At first it sounded like it had something caught underneath just hitting the metal.  Upon looking underneath there wasn't any visible problem.  Now it is hard to start and won't stop making this clunking noise.  No smoke is visible and the noise is the only problem.  Any ideas as to what this can be?  Did I blow the engine?  I might have hit a tiny stump, but I'm not sure.  Thanks for the help...

Answer
Hi Steven,

Remove the spark plug so you can turn the engine over by hand while you look and listen for the noise.  If it seems like it is still coming from inside the engine, then there may be internal damage.  Especially if the engine is old or if it was low on oil.

Let me know what you find.
Michael