Small Engines (Lawn Mowers, etc.): Briggs and Stratton will not start, engine model type, briggs and stratton

Question
My Briggs and Stratton will not start. If you take the spark plug out the motor will crank freely but as soon as the spark plug is screwed in the motor will not crank.

Answer
What is the engine model, type and code number?

Is the battery fully charged?  Have you dis-connected and cleaned the battery terminal posts and cable ends with a wirebrush?  I've fixed a lot of starting problems just by charging the battery and cleaning the connections.

Please send me the engine information so I can look up your engine.
Eric