Piedmont, Have you looked into the battery? Same situation on my 2520 last summer. Mowed, went in for lunch and would not even turn over when I came back. The battery operated the fuel pump (clicking sound when key is on) and also operated headlights. However, wouldn't crank machine. Took the battery in for a load test and it was toast. 1 new battery and I have not heard from it since. I would try that.
Randy, I cleaned the terminal and put it on the Battery Tender and it charged and it still won't start. Was your 2520 making a loud sharp noise when you tried to start? It sounds like the starter but if yours made the same noise I go the new battery route first.