Small Engines (Lawn Mowers, etc.): engine wont start without jumping off, craftsman riding lawnmower, jumper cable

Question
I have problem starting my 12hp craftsman riding lawnmower. I've charged the battery full power, turn the key on and the engine starts to crank and then stops, then clicking noise happens and won;t do anything. Some times it won;t even make a noise.

I took jumper cable and attached to positive cable on battery and touched the large nut on the starter, turn over better then stops and nothing happens. Can then turn the key and engine starts. If I take the cable off the battery before i turn the key nothing happens.  It seems to work better when I have the jumper cable attached to the batter rather than using the battery by itself.  I mow for a while then when turn the engine off and try and restart it most of the time the engine will turn over a couple of times but not start.  Then I connect the jumper cable, touch the start turn the key and it starts with no problem.  What up with that?

Answer
Have you dis-connected the battery cables and cleaned the battery terminals and cable ends with a wirebrush?  Sounds like there may be a poor connction.  I have fixed many, many starting problems just by cleaning the connections.

Let me know what happens.
Eric