I have a Lawn Boy 10515.  It starts on the first or second pull each time. The engine continues to run perfectly.   However, if I shut it off after it has been running, it won't restart.  I discovered there is no spark after the engine is hot and shut down.  After it cools it starts back up easily.   Any ideas?  I am stumped.  Could it be as simple as a bad spark plug?  I will appreciate any suggestions.  
	
		
			
		
		
	
			
			 
				