I have 917.387321 craftsman push mower (1998). Tonight I pulled the shroud off, cleaned the engine (wiped it down) of dirt/grease, etc. I put shroud back on, drained and put in new oil and replaced the air filter. Now, when I pull rope, it jerks back out of my hand about half-way out. If I pull rope slow, I can fairly easily pull rope way out, but pulling fast/hard on it and the rope wants to jerk back. If I am at all successful at getting engine started, it sounds like it's not quite running at full power, and occasionally a minor backfire. When I release the brake handle, the engine stops NOW, rather than the usual 1 or 2 seconds it normally takes. If I remove the shroud, and put my hand on the flywheel (which has the magnet on one side and a balance weight embedding across from it), I can easily rotate it around...no resistance. I don't understand why all the sudden this is occurring. I had started the engine just minutes prior to warm the engine before changing the oil. I've never had any issues with this mower until now all of the sudden.