Repairs HRX2173HYA wont start.

I bought this mower less than 2 years ago and only run it around the edge of my yard so that my rider can make corners and such. It has less than 5-10 hours on it, I have always stableized the fuel when storing it for the winter. When I got it out last week to fire it up, it won't start. I checked the plug and have good spark. I dropped the bolt out of the bottom of the carb bowl and I have fuel at least in the carb. Don't know why it won't start. Any ideas??

Repairs HRX2173HYA wont start.