Zero Turn Mower. I'm stumped.

I've got a Craftsman riding mower that is so old.....I'd be curious to know what Noah done with the other one! I put a fuel shut off valve between the tank and carb. When I'm done mowing, I cut the valve off and let it run out of gas before I shut it down. Haven't had a carb problem since. I run non ethanol 91 octane in all the little motors and keep Marine Stabil in the jugs.