Small Engines (Lawn Mowers, etc.): Starter engages when ignition is in On pos., john deere 345, transistor ignition

Question
I've got a John Deere 345 with a Kawasaki FD590V liquid cooled 18 hp engine.  Its got the transistor ignition and I just spent a day and a half replacing the water pump on the front of it.  I ran it today for about an hour and a half with no problems and then it cut off on me.  With the key in the ignition in the on position the starter engages and turns the engine.  This is not in the crank position but rather the on/running position of the ignition.  Something must have gotten loose or I don't know.  I did have to take the ground wire off for the battery when unbolting the engine to fix the water pump but I wouldn't think the ground would do that.  Has anyone come across this before?

Answer
It sounds like you may have lost your ground go back and find the grounds be sure that they are tight and clean.  The other thing would be the ignition key switch I would start with replacing that.  The other thing to look at is, is there a circuit board on the unit.  You could have something wrong with the circuit board.  The best thing to do at that point would be to take it to a dealer and have the circuit board tested.  I hope this information helps you out if not please get back to me more questions.  Good luck on your project.