Small Engines (Lawn Mowers, etc.): Riding mower wont start, starter fluid, carburator

Question
I have a 3 year old Craftsman, 17hp riding mower. It has never failed to start til today. Plus, it's worked fine all summer.  Til today. It cranks, but won't start.  Has good spark.  Replaced plug anyway.  Also replaced fuel line which was rotted (in only 3 years?)  Sprayed starter fluid into carb intake, but didnt help.  Doesn't even sound like it's firing at all, even with starter fluid. It just cranks and cranks and cranks.

Answer
 Hello Sheldon:

 What is the Compression? If the Compression is 70psi or Greater, then Recheck the Carburator. If the Compression and Spark are Good, then the Carburator is All that can be the Problem. Did you Use the Starter Fluid While Cranking the Engine? Send me the Make, Model, Type and Code Numbers Off of the Engine, Please. With these Numbers I can Locate a Breakdown of the Engine and Better Assist you. Hope this Helps. Let me know what Happens, Please. I enjoy knowing the Outcome. Thanks.

 Good Luck

 Respectfully

 John