When sitting in the seat, ignition turned, clutch/brake depressed, Ammetter indicates strong battery. But that's it! Nothing else make a noise :(

Hi,
Check the solenoid thusly. Lock brake and put in neutral. Open hood and with a length of wire(14 awg would be good) touch the large post with the wire from the battery with one end and the small post with the smaller wire(probably red) with the other. This should trigger the solenoid.
It tells you a number of things potentially. If the solenoid clicks and the engine turns over(starts if the key is on) then it is somewhere else on the machine(possibly the keyswitch.) If it clicks and nothing happens, then the high current circuit is no good and it is time for a new solenoid. If it does not click, time for a solenoid as the trigger circuit is "fried." If it clicks and you hear the starter try to engage but the engine won't turn then there is also a problem there. If it clicks and the starter whirrs bit nothing happens, check to see the battery is not connected backwards or the starter pinion is not shot.
That should get you started.
Peace,
Clarke

Thanks Crigby, I used a piece of 12 gauge wire to connect the 2 post. Got a lot of sparking and the engine turned. I had the keep off at the time. What's next?

Sorry, I meant I had the Key off at that time.
I pulled the back of the keyI pulled the ignition harness off the Igrnition switch and cleaned it with an electrical spray, but it did not help Still nothing happens if I turn the Key.

Okay Great. I turned the key on and jumped the 2 cables from the battery to the starter and it started right up.

But I still don't know what part needs repair or replacment. Can you help?

Check the safety switches there is something not letting your switch power the starter

Hi,
I did not mean to do it between the big posts or to the starter. The solenoid should have two large posts and one small post. Jumping from the side with the battery to the small(trigger) post tests the solenoid. The solenoid is an electromagnetic switch that uses a small current to to trigger it to move a large current when triggered.
Peace,
Clarke