Starter

Yesterday when mowing with 247.288820 rider I experienced a starting problem. My starter will not engage. I can hear the solenoid clicking but nothing at starter. I ran hot wire to starter and nothing happened. After towing to garage the starter was removed to bench where I again supplied 12v, still nothing. The gear that pops up to engage the engine flywheel is free but seems weak. Knowing nothing about starters I plan to open this one up to smell around hoping something jumps out at me. Anyone have a suggestion as to what I should see/look for?

Starter