Incredible, I had this same problem yesterday. After many attempts I was successful, but I can't say it's an optimal method.
Remove the C-ring holding the 3 armed "sprocket" and lift it off it's rod. The sprocket arm is in the locked position. Straigthen this assembly.
Put the spring and its assembly back in the groove with the sprocket assembly out straight , not bent the way you found it. Take a pair of locking pliers and secure the bottom end of the spring to the housing, Not so tight that you damage the spring.
Take a thin screw driver about 3/8' wide and insert between the front of the spring assembly and the housing wall.. Use leverage to compress the spring. Try again. Work from the inside edge of the housing. I was able to squeeze the spring and the "sprocket" arm straightened out. I carefully slipped it over the rod, and then took another locking pliers and lightly secured the front end of the spring.
Then I replaced the C- ring, attached the plastic frame parts, reattached to the chain saw body. Tested it and it worked fine.