Small Engines (Lawn Mowers, etc.): Briggs & Stratton will not start, mtd yardmachines, briggs stratton

Question
B&S 135202 MTD Yardmachines Tiller.   One day running great, then it quits - valve sounds wrong.  Exhaust valve stem collet notch appears machined off - slowly machined the notch away.  It did not break off - no shavings or cap, just a metalic sheen/sludge to oil.  Never seen this before.  
I replaced the valve.  I removed the Carb/gas tank as an assembly - I replaced as an assembly.   I get spark when pulling the starter chord.  I get fuel in the carb (if tiller leaning back, it puddles slightly in rear or carb).
It will not fire.  Even with starting fluid.  There is compression ~ around 30lbs?
Can't figure out what I did wrong?

Answer
 Hello Andrew:

 Did you Lap the Valve in? If No, then that is the Reason for Low Compression. Did you Set the Valve Lash(clearance between the Valve Stem and Tappet). This will Also cause Loss of Compression. Compression Needs to be 70psi or Better. Anything Below 70psi and it will not Operate Properly. Send me the Type and Code Numbers, Please. With these Numbers I can Locate a Breakdown/IPL of the Engine and Better Assist you. Hope this Helps. I am here if you Require more Assistance. Let me know what Happens, Please. Thanks.

 Good Luck

 Respectfully

 John