Small Engines (Lawn Mowers, etc.): mower wont start, briggs and straton, hp briggs

Question
i have bolen mower with a 17 hp briggs and straton ohv engine, the mower won't start, thought it might be the battery, when i turn the key sometimes it will turn over other times it just clicks, when i pulled the spark plug out it turns over without a problem, when i put the plug back in it goes back to not turning over or partly turning over. i had no problems with this mower until i changed the blade belt due to it breaking ( my son ran over a can and the belt snapped, according to him the engine continued to run after that without any problem. any help will greatly be appreciated

Answer
It sounds a little like the installation of the new belt may be causing excessive drag on the engine.  This could be caused by the incorrect length of belt, incorrect installation or something causing the belt to not fully disengage.  This would require extra amperage to turn the engine over which may not be available if the battery is already weak or the connections are not perfect.  Hope this helps.