Small Engines (Lawn Mowers, etc.): Suspected carb problem., craftsman model, compression stroke

Question
I have an older (purchased in 94) Craftsman model 502 rear engine riding mower (Murray). 10hp Briggs motor. My troubles started with the symptom that the engine would not turn over. Cylinder would get to the compression stroke and just stop. Suspected battery, starter motor and solenoid all replaced w/new components with no change in condition. Removed spark plug and engine spins freely with no apparent clearance issues. Removed cylinder head to inspect valves and found no issues. Did notice heavy carbon deposits so cleaned head. This appeared to resolve the issue and the engine now starts but surges at all speeds and will not idle. Suspect problem with governor (fly weights), Bad governor spring, Carb issue or some mix of the above. Your guidance is appreciated. Would also like your confirmation that heavy carbon fouling of the head will cause over compression keeping the engine from turning over.  

Answer
 Hello John:

 The Carbon Build up Could have been the Problem. I have Found Out that Briggs and Other OEM's are have Valve Lash Problems that are Causing the Problem you Described Also. Is the Plug Gapped to .035in? Adjust the Air Mixture Screws. If Adjustment Dont Correct the Problem, then Clean and Rebuild the Carburator. Hope this Helps. I am here if you Require more Assistance. Let me know what Happens, Please. Thanks.

 Good Luck

 Respectfully

 John