Hi and welcome to the forum
You know it is a carb problem. For some reason, I would guess, the float is sticking.
When runs 45 seconds it is just burning the fuel in the bowl and not getting any new gas. Next time this happens tap, NOT beat, on the bowl with the handle of a screwdriver. Again with give nice taps, you don't want to dent or break again thing.
If that works you may want to get a rebuild kit for the carb.
BG