Snapper zero turning with 25 hp Kohler when the motor is running start the blades it cut off What is it?

i would check the safetly switch ( if you can find it) it usually cuts off the mower if someone isnt sitting in the seat ( for safety) and your just may not be recognizing that someone is sitting there|||On my dixie chopper,you have to have the brake off and the drive handles in operating position to engage blades......George|||Since it happens when you engage the blades my guess is that is not the blade safety but the reverse. Most mowers will not let you go in reverse with the blades engaged. The lever for direction should have a switch, probably just a metal strip with a wire attached. When in reverse it shorts out killing the engine. Try unplugging the wire and see what happens. If that fixes it just find out why it is shorting, may have just come loose.