Small Engines (Lawn Mowers, etc.): Lawnmower noise, briggs and straton, engine noise

Question
My briggs and straton push mower starting making this LOUD clicking noise and is vibrating more than normal.  I have checked the blade and it is not rubbing on anything or catching on anything. It sounds and feels like something with the blade but I can't see what it is.

Answer
The things to check are the pulleys to see if they are damaged, The belt to see if there is any damage, the spindle shafts and bearings and the clutch.  Does the mower make the noise when it is off?  If so it may be an engine noise you are hearing.  If the blades have to be engaged to hear it follow the mechanism from the engagement point to the blades.  More than likely it's the spindles or  pulley.