For the time being replace the solenoid with carburrettor bolt # 691511 and copper/ fiber or aluminium washer
When you shut down run the throttle to minimum then turn engine off .
Occasionally you might get a backfire from the muffler , it won't hurt anything other than your nerves .
Just this week,my mower,the Husqvarna 42175 ZTR,powered with a 19hp Intek B&S,,just up and quit ,at the back of the one acre MIL's yard! A quick diagnosis led me to believe no fuel. Fuel tank was full,fuel valve was on "ON",so what? The pesky anti-backfire solenoid carb valve,maybe? Turning the key on and off produced no 'click' from the solenoid,but it had juice to it.( Before reading on.. please be advised, I do not sugguest defeating ANY safety features at all!) I removed the solenoid,plugged it back into the harness,turned the key and no retraction of the pin valve. Warning:a non-recommended fix follows. I took my side cuts and cut the tip of the needle valve off. (Horrors) put everything back together and proceeded to mow without further ado for the next hour,or so. The ignition switch has the magneto kill switch incorporated into it so no issue with shutting down. Is this OK or am I in deep trouble with the EPA? :-D.