Assuming you've got the cover off and the spring is still in the right place (it's a bit of a beach to get that back in place!):
This is more difficult to decribe than it is to do.
Hold the starter drum down with your left hand and pull out a few turns of starter cord with your right. This will tension the spring. You'll have to experiment to get the right amount, but 6/7 inches is probably enough. Now, hold down the drum firmly so it can't recoil and pull some of the cord back through the hole it exits the cover through. You'll have to hook it with a screwdriver or something. Hold this piece very tightly and locate the notch on the edge of the cord drum. Use the cord in this notch to rotate the cord drum, adding more tension to the spring. After a couple of turns, hold the cord drum down firmly again and pull the cord back out of the exit hole. It will have twisted a bit, but this is not a problem. Release the drum carefully and the cord should be pulled back in - fully tensioned.
Wes, July 2009