Just removed deck to sharpen blades. Replaced everything and rode it back to shed. Went to use it and it won't keep running more than 2 secs. Almost like a safety switch isn't working? My foots on brake, PTO (blades) disengaged, turn key and it runs but just as quickly stops. Does same thing over and over? Must be getting fuel and it wouldn't even fire up when turning the key if blades or seat switch weren't working. Is there a switch on the deck I don't know of?

There is a safety switch that prevents starting if blades are engaged, this may have failed. Check you manual for location. Why would you remove the deck to sharpen the blades,way too much work.