Small Engines (Lawn Mowers, etc.): Toro mower will not crank, hand lever, recoil

Question
Toro recycler 22 inch self propelled mower with 6.5 Hp tecumseh engine. 2003 model 20016 . Always starts and ran great 3 days ago.  Today when tried to pull the start feels like there is too much compression or is out of time.Very hard to pull. Too much recoil. Never has been run low on oil. Never smoked.  Is there a flywheel key like on B&S motors? The flywheel brake that is activated by the hand lever works fine. Seems to be making a knocking noise. The blade is not hitting anything and is tight.Any thoughts? Bill

Answer
The first thing to do is pull the plug and see if oil or gas come out of the cylinder. And of course check the oil and smell it for gas.  Next would be the flywheel key.  I'd also pull the blade off even though it is tight, just to be sure.

Did you hit anything like a stump or root?  It hasn't been stood on it's nose has it?