Whip out the plastic and go get a NEW MOWER. Seems to be the norm now days.
Every time the wife gets a flat tire she wants to go buy a NEW vehicle. After she calls me to come install her spare. (and I most generally fix my own flats)
We live on dirt/rock roads and have to use at least 6 ply...
Looks like the OP has ghosted us but:
I repair my own lawn tractor/trailer tire flats.
I've had problems locating really slow leaks in tubeless tires also, sometimes even using a water tub will not show a aggravating seep.
I have two spray soap bottles. One has a large dose of Dawn dish soap...
Good to hear you got it going.
Another weird one I could not believe.
I received a free old model Horse tiller with the later model Tecumseh engine with no carb on the engine. It had the 2-3 inch intake manifold steel pipe still attached to the head.
Sometime later I gently pulled on the start...