I could not fix that lawnmower engine.

However, I can fix a rewind starter pull cord. I've repaired a few of these, and the last time I attempted it, I took photos.

Lawnmower pull cords break all the time. The cord gets wet, it sits in the sun, and it is subjected to a rough series of yanks every weekend in the summer. The cords are under a lot of stress. 

Some lawnmower cords end up as alcoholics. Others snap.

Lawnmower cord breaks provide a short, fun repair project that will temporarily interrupt your lawn mowing duties. 

I'll try to guide you through this with these words and pictures. 

First, some background: A lawnmower pull cord is a lot like the string on a spinning toy top. At rest, the cord is coiled up around the outside of a round wheel called a pulley. As the cord is pulled, the pulley spins in place. This spinning pulley is attached to the main motor shaft, which, once it is warm and operating, makes the whole machine fire into life. 

This string-activated starter pulley does not continue to spin as the engine runs. It is outfitted with a bunch of little teeth, which lock onto the motor shaft only while the pulley is rotating at a faster speed than the shaft.

These are the steps to replace the cord: 

1. Buy some new cord.
2. Open up the housing which holds the spring-loaded starter pulley. 
3. Remove the starter pulley (if necessary)
4. Remove the old cord 
5. Attach new cord to pulley, probably with a knot. 
6. Wind new cord two or three times around the pulley. 
7. Thread the cord through the hole in the metal pulley cover. 
8. Re-attach the pulley to the engine motor or clutch 
9. Fasten the metal cover. 
10. Give the new cord a few pulls to test the recoil. 
11. Reattach the little plastic "T" pull handle. 
12. Mow.

Detailed instructions:

I found 1/8th inch cotton cord at Home Depot. The bright yellow cord was the cheapest, so that is what I got. Steel guitar strings would never break, but they would probably rust.

Opening up the starter housing was not straightforward. On my Craftsman Eager-1, I had to remove the small plastic gas tank to get access to the bolts which hold on the starter string housing.

I think all of the bolts were 10mm.

Please continue reading page 2 of Easy, Illustrated Instructions on How to replace the starter cord on a lawnmower.