starter recoil spring for lawnboy model S21 Bsn sn. H059bo157?

lawn-Boy model s21BGN sn. H059bo157 starter recoil spring. I don't have the old one, but took one off of a tecumseh eng 4.0. and was also given a part nbr. 92-4935(Toro)/ I'm not sure how to cross reference the number or if the one out of a tecum. 4.0 will work. Can you advise if spring(s) are corrrect and how to install?

Billy