Small Engines (Lawn Mowers, etc.): Craftsman B&S 7.0HP has lost power, briggs and stratton, clump of grass

Question
I have a Craftsman mower, rear-wheel drive, with a Briggs and Stratton 7HP engine.  Engine model 128602-0304-E1.  The mower has worked fine until recently when it seems to have aquired a couple problems at once.  The engine seems to have lost alot of power.  On the driveway, it seems to run fine (although rpms may be slightly low or it may be my imagination) but once I hit the grass at a normal pre-cutting height, the mower immediatly bogs down and frequently stalls.  What I had loved about the 7HP engine was that it could cut through taller grass without problems.  While mowing grass, the engine also seems to knock.  
The other problem it has is when I want to stop the mower and release the control bar, the mower often continues to run for several more seconds until it finally dies.  I have changed the spark plug and air filter and squirted some carb cleaner into the carburator.

Thanks

Answer
 Hello Pat:

 It Sounds like the Carb Requires Cleaning and Overhauling. I Looked at the Carb Listed for your Engine and it is of the Type that is Non Adjustable. Has this Mower Hit a Large Clump of Grass or Other Object that may have Damaged the Flywheel Key? Hope this Helps. Let me know what Happens, Please.

 Good Luck

 Respectfully

 John