Small Engines (Lawn Mowers, etc.): Fuel Problems, compression issue, exhaust ports

Question
I have a Lawnboy walk behind mower, model #10330, that won't stay running.  It has been setting for a couple of years.  I am getting spark and can get it to run for a few seconds when primed or I fill the carb with carb cleaner.  I've cleaned the carb and can only keep the mower running if I keep spraying carb cleaner or fuel into the carb.  Once the carb cleaner in the fuel bowl is used up, the mower dies.  It sounds like a dirty carb, but I have soaked it and cleaned all of the openings with a wire.  The fuel line and screen filter in the gas tank are all clean and clear.  I haven't replaced the primer plunger yet, although it doesn't appear to have any holes or cracks.  My thought was that a small crack or hole in the primer plunger would cause it to lose prime and not get fuel.  Is that a possibility?  What next?  

Answer
If you can only keep the engine running by spraying fuel into the carb and you are absolutely sure the carb is clean, I suspect you have a compression issue.  Excessive fuel can help seal the rings when there is a problem with them.  I recommend you remove the muffler, inspect the exhaust ports for carbon build-up and have a good look at the rings, piston and cylinder through the exhaust port.  Let me know what you find.