Put Slime in the tire, drove around for 10 minutes, parked, couple days later the tire was down from 14 to 9 PSI, noticeably low. Pumped it up and immediately mowed the lawn for 25 minutes, 2 days later it doesn't look flat.
Doesn't really matter the tire has dry rot and a new one is on the way. Last time I did a tubeless 8" mower tire was terribly easy after the bead was broken loose. The depression in the rim was so deep the tire practically mounted itself bare handed. Mower tires are very thin walled and flexible.