Lawnboy 101662 Self Propel issue

Last fall, I acquired an old Lawnboy 101662 mower, which I tuned up and stored to sell this spring. When I took it out of storage, the self propel was extremely weak and the spring on the cable was not decompressing. It was almost like the cable had stretched over the winter, because I know that the propel worked fine before. Any ideas? I would love to get this thing working and sold as soon as possible. It can't be the belt, because the spring on the end of the cable is not pulling enough to engage the gears.
Thanks, Lincoln