I do have a Craftsman 6.5 hp 21 lawn mower equiped with ab Briggs & Stratton engine.
I cannot pull the starter cord to full extension, it starts to block and it feels as it hits back. Grey smock is coming from the engine it. If I remove the plug I have no problem to pull, so I guess it is not the a deformed crankshaft.
Any ideas?

Renate Raeder, November 2006

Have you hit something hard recently?
With the spark plug wire OFF! Check to see if the blade is tight to the blade adapter. If the blade will wiggle replace the adapter. If it's not the adapter, the flywheel key may be partially sheared. Either of these conditions will cause "out of time" symptoms, such as kick-back.

Rick, November 2006