Toro LX500 wont start

Recently I was given a Toro LX500 which has Kohler Courage 22hp engine. It hasn't been used in 3 years and would start. I sprayed a little carb and choke cleaner in the air box and it fires up but won,t stay running. Last night I pulled off the carb and cleaned it all up, changed the air and fuel filter and put in new plugs. After all that was completed it still wouldn't start. I then drained all the fuel and replaced it with new fuel and it started right up on the first turn of the key. I shut it down and restarted it several times with no issues. Today I got out to the garage and it wont start again. Any help or ideas what to check next would be a great help. Thanks Mike