I pmed you back, thanks but I got to the dealer.
I had to noodle the part out when the sol. was energized. I figured out it was normally extended and powered for a few seconds to shut it off. Seems a bit backwards, however it makes more sense because you can still run the tractor without it.
It looks like the 2810 has the same set up and I would guess the 4110 does also since the 3510 and 4110 share the same book.
If your key wont shut her off, check power to the stop solenoid. It SHOULD be 0vdc when the key is on, 12VDC off for about 15 seconds, then 0VDC.