Small Engines (Lawn Mowers, etc.): 18.5 briggs no start, valve adjustments, compression test

Question
My 18.5 Briggs ohv model/31P777  type/ 0296E1    code/ 040119ZE
ran fine until I started it up and it backfired then cut off and will not start. The top valve was way out of adjustment so I adjusted it and still no start.It also cranks over easier now so I am wondering about that as well.I took the camshaft out to inspect and it looks perfect. I FORGOT to mark the camshaft were the gears line up on the crank gears so I researched and found that I needed to line up the DOT on each gear so thats what I did and I hope that was right. Anyway I got it back together and still does the same thing even after valve adjustments. Help me please.

Answer
do you have compression?  meaning did you do a compression test?  

What did you adjust the valves at?  When you adjusted them was the piston at TDC  (Top Dead Center)

Do you have fire at both spark plugs?

Have you checked you ignition timing key that is located in the flywheel.  These are the areas I would be looking.