Most if not all tracts from the mid to late 90's on have a solenoid on the bottom of the carb that prevents a backfire when the engine is shut off. They usually work without issue but can go bad and cost a lot to replace if you don't have a good used spare. This shows how to get rid of it entirely using old parts off a push mower. This applies to Walbro carbs found on Kohler engines but may work on others as well.