Small Engines (Lawn Mowers, etc.): Craftsman 5hp mower clogs & stops, craftsman eager 1, mulching blade

Question
I have a 5hp 22" craftsman (eager-1) with a mulching blade.  Lately I absolutely cannot cut the lawn unless I rig the rear bag door open or it chokes on any amount of grass (example: after mowing about 2 feet of grass just 2" shorter than it was).  Replaced air filter and blade with no change.  Engine seems good, front drive works great.  When I tilt it over and manually turn the blade, there is some non-constant resistance, even when I disconnect front drive belt from shaft (in case that's where the problem was).  

Any ideas?  Would like to avoid borrowing $$ for a new mower.

Answer
Hi Eric,

A dull blade was what I first suspected but you have eliminated that possibility with a new blade.  If the spark plug is okay and you have tried adjusting the carb, I would then suspect a worn engine, especialy if it is old.  A compression test would confirm this.  The resistance that you feel when rotating the blade is the engine's  compression.  

Let me know how you make out,
Michael