Ariens Apex 60 dies after engaging deck

[bertsmobile1]

keep in mind that he gets 25 yards of normal mowing before it "sputters and dies."

Which is what makes me think it is a main jet problem of some sort as the mower will be running on the idle circuit until a real load is put on the engine.
Doubt it is a safety switch unless thee is a loose wire flailing around from the wind flow / vibrations of the deck running .
It is also the sort of thing that happens when you have some water in the bottom of the float bowl.
Usually a bad head gasket will cause the engine to splutter the instant the blades are engaged then smooth out as the throttle closes back down a little
A bad / worn / stretched governor spring will also do this but usually it will be associated with slow running
corrosion around the throttle shaft can manifest in similar symptoms .
But for the first place lets see if it is throttle, electrical or mechanical .