Small Engines (Lawn Mowers, etc.): john deere z225 ignition problem

Question
I have a John deer z225, 18.5 HP Briggs engine. I've had no issues this season until now. Using it the other day, I cut about 1/2 of our 2 acre yard. Everything was fine. I shut it off to move something, now it won't start. PTO is off, parking brake is on, steering arms are open. Thinking it was the starter motor, I removed the motor cover. When you turn the key, the starter motor "clicks" & the gear engages the flywheel gear then stops dead, & just hums. I replaced the starter to try it, it does the same thing.

Thanks in advance,
Doug

Answer
Did you have the battery load tested at you local auto parts store to see if the battery is bad?

Did you dis-connect the battery cables and clean the battery terminals and cable ends with a wirebrush?  I have fixed a lot of starting and charging problems just by dis-connecting and cleaning the connections.

Eric