Dad called me and told me he fixed the lawn mower. He also gave me the rest of the story.
If I understood him correctly they bought it from Walmart as used, repaired, and as his. He said it looked like it had never been used more than once. He fixed it by removing the water from the carburetor. Maybe it originally belonged to a DUer who was anti-gas?
In a comment that would surely endear him to feminists on DU he said that they now had his and her lawnmowers: the big one with the seat was his and the push mower was mom's.