Small Engines (Lawn Mowers, etc.): 14 horse Briggs kicks back, wont start., compression stroke, valve adjustment

Question
This is a Wards Signature 2000 with a 14 horse Briggs (28707) and Hydrostatic drive.  It's old...15-20 years old. When trying to start, the first compression stroke comes to an abrupt halt. So I let off on the key to let it bounce back a little, then hit the key again and after "rocking it" I can get it to go over the compression stroke.  It used to start that way and run fine, but now it won't and sometimes kicks back hard with a pop like the ignition timing is way early.
  This has I/C ignition.  Is there still an aluminum key on the flywheel that can partially shear and mess up the timing?
  It isn't a weak battery....I have charged the new battery and even jumped it with my pickup and it still hits the compression stroke like a brick wall.  I even tried a different starter that I know was working ok previously and it acted just the same.
  Thanks for your help. Bill

Answer
Bill

You may need to adjust your valves having them out of adjustment will cause a engine to start hard  almost like the battery is weak.It is not your starter or the flywheel key may be sheared but most likely it is the valve adjustment. To set the valve adjustment remove the spark plug and let the piston go to Top Dead Center which is when the piston comes up to the very top and it starts to go down this is TDC and it has to be on the compression stroke.Then adjust the valves to 00.10 to 00.15 on the exhaust and also on the intake.