I have a Sears Craftsman 2.0 mower. I hit a rock and now the mower is making noise. It still operates, still cuts, but the pullstart wire vibrates like crazy and it sounds like something is striking underneath. The blade looks okay and I don't see any apparent damage underneath. Any ideas?

If you hit a rock it doesn't take much to bend the blade or even the shaft. Take the blade off(Disconnect plug wire first) and inspect it on something level. If in doubt, try a new blade.

Fortunately, usually the blades bend first. If carefully checking blade doesn't show a problem, before I bought a new blade, I would put it back on, and turn it and see is it goes up and down because the shaft is bent. It is extremely important to have the spark plug wire off any time you have your hand under the deck. Maybe even pull the plug to keep the engine compression from swinging the sharp blade into your hand. It may be easier to see with the mower on a flat surface looking in the grass chute. Watch the shaft too. Even a small bend in the blade where the bolt goes through, can cause a big wobble.

I have a Sears Craftsman 2.0 mower. I hit a rock and now the mower is making noise. It still operates, still cuts, but the pullstart wire vibrates like crazy and it sounds like something is striking underneath. The blade looks okay and I don't see any apparent damage underneath. Any ideas?
... and after I let the mower set a few days, it would start without the noise but with little power. Haven't had time to take it apart but have experienced similar problems with other mowers and had to remove the flywheel to replace the aluminum crankshaft key which bends or shears off when the blade hits a 'brick wall'. Key prevents serious and costly engine damage but results in serious timing issues ranging from can't start to starting with lots of noise, smoke, etc.