Try squirting some PB Blaster or other penetrating oil in thru the spark plug hole, then see if you can turn the engine thru several turns, by hand. It may have rusted up in the cylinder when stored. I fixed one by taking off the belt cover, then turning the pulleys back and forth until it freed up.
Sometimes, when you put a machine away, the piston stops at the point where a valve is open, which allows moisture and corrosion to form in the cylinder, and won't allow it to move when you pull the rope.
another thing that happens, if you let the rope snap back in, it can tangle up under the flywheel housing.

What's the Sears 917.xxxxx number.
One help in solving engine problems is to know what engine is involved!
IF it's an OHV engine, possibly a valve is stuck open preventing the piston from moving all the way up.
IF it is OHV, remove the valve cover and see if a rocker arm is excessively loose.

I have a college kid (aka "Farmboy") who helps me out around the place - feeding horses, supplying muscle, etc. (Have 51 acres)

He showed up Sunday and asked why the tiller was out - I told him. He walked over, put it in gear, turned on the gas (all of which I'd done) - grabbed the starter and pulled. Twice. Engine fired up and I've been using it.

As he said . . . "Sometimes the starter just gets stuck and you have to pull through the snag." (Yeah, like this old woman has muscles to 'pull through')

But it works, have broke the garden spot up twice, will do it once more tonight and get the tomatoes out. (Later this week comes the beans, okra, corn . . .

August/September will break out the tractor, plow, disks and do it right.