Small Engines (Lawn Mowers, etc.): Mower wont start, craftsman riding mower, bridge rectifier

Question
I have a Craftsman riding mower that was running fine.  After changing the battery I was able to use it 1 or 2 times again.  I could feel the starter solenoid knocking so I changed it and the key switch too.  The battery shows 12 volts when the key is off and 2 to 3 volts when the switch is on, but the engine will not even turn over.  Any ideas?  Thx

Answer
The battery is discharging through the diode.  There is a wire that charges the battery one way and does not let it discharge the other way.  It also changes AC in to DC current.  Find the diode in the system and change it.  It may be no more than a bump in the wire or a bridge rectifier.  Good luck.