Small Engines (Lawn Mowers, etc.): 18.5 ohv in a LT 1080 cub cadet, briggs stratton, series numbers

Question
I have a cub cadet bought in 204--warranty died last year of course. I have never had a problem with the engine--ticked like a clock. I was mowing along with not a miss or bobble when I shut her down to move a vehicle. Jumped back on and the engine turned freely (seemed too freely) but would not hit a lick. Pulled the choke and got a couple of small backfires only. Pulled the plug today and checked the compression only to find NO compression. Has anyone encountered this problem? Valve? I have never torn down one of these engines but may be about too. Anyone have any ideas or a path to an online engine repair manual?  Oh yea--its a briggs & stratton 18.5 ELS 500

Answer
Hello Frank:

I Have Seen this Problem Several Times Over the Past 5 or So Years, but it is Not a Common Problem. Send me the Model Numbers Off the Engine, Please. With these I can Locate the Proper Manual and Better Assist you. The Numbers you Sent are the Series Numbers. Sometimes I can  Use the Mower Model Numbers to Locate the Engine Model Numbers. It Sounds Like the Flywheel Key May have Sheared because the Flywheel Nut Loosened. That is a Good Case Scenario. It can be a Valve Spring Keeper Broke or Jumped Of the Valve Stem. A Dropped Valve Seat and Several Other Causes. The Engine Model Will Assist me in the Suggestion I give you. Hope this Helps. I am Here if You Require More Assistance. Let me Know What Happens, Please. Thanks.

Good Luck

Respectfully

John

PS: I am Allowed to Answer 10 Questions a Day. If you See I am Maxxed Out, then Try Submitting you Question at or Just After 9pm EST (US). My New Day Starts then. Thanks.

Respectfully

John