Very simply put, and correct me if I'm mistaken, you would just "interrupt" the ignition wiring with an in-line single pole single throw switch that basically "cuts" one of the wires that complete the "key switch circuit"
When the switch is "on" power travels through the circuit...when the switch is "off" no circuit...
That's my understanding of what you'd need to do, but more "wiring/electrical" knowledgeable folks please chime in if there's a better way.

On another note you could actually "cut" one of the wires and put some type of connectors on the ends and simply "unplug" your connectors to accomplish the same thing. When you want to use the tractor, don't forget to plug in your connectors...

 

Kill switches normally go in one of two places, the positive feed to the ignition switch or the feed from the switch to the starter solenoid. Most people hide them and use a keyswitch as the means of disconnecting the circuit. On equipment with electric fuel pumps, sometimes they are installed on the positive feed to them. Something as simple as pulling the fuse can work as a kill switch too. If you use a double pole switch, it can also be wired in to the starter solenoid so that if someone tries to start it, an alarm goes off.

 

when I setup a switch I put it in the starter circit. I PUT A FUSE IN THE WIRE THAT ENGAGES THE STARTER THEN RUN A WIRE FROM THE STARTER SIDE OF THE FUSE TO THE HIDDEN SWITCH FROM THE SWITCH TO A GROUND SO IF SOMEONE TURNS THE KEY THE STARTER DOES NOTHTHING AND YOU HAVE A BLOWN FUSE TATTLE TAIL. JUST REMEMBER TO FLIP THE SWITCH AND KEEP SPARE FUSES OF THE CORRECT SIZE.

 

A friend of mine had a couple inline switches in his old Toyota pickup. The truck was a piece of crap. The old ones came stock with a button on the dash that you had to push before you could start it and then he added an inline toggle (two way throw). He once told me how to start his truck and I was on my cell phone sitting in the truck and had a hard time starting it. After a scuffle at a bar a few thugs tried to steal what they thought was an employees truck from the employee parking. The truck made it about 20 feet into Huntington ave in Boston where the fuel ran out of the fuel lines and the fuel pump did not engage (two way toggle). Just enough noise and a scene for the guys to jump out and run away. We were laughing until the BPD showed up and gave him a ticket for being illegally parked. Way to be Boston.

I see no reason why people would not take the few minutes to add something like this to the thousands of dollars they have sitting in thier back yards.

If I leave a mower somewhere in a backyard out of sight to go grab lunch, I will shut the fuel off, release the break, pull a fuse, engage the blades and pull the key(thirty seconds of time). By the time someone figures out how to start it and finds a flat fuse to replace the one in my pocket if Im not back from picking up lunch or parts they deserve they mower.

 

On another note you could actually "cut" one of the wires and put some type of connectors on the ends and simply "unplug" your connectors to accomplish the same thing. When you want to use the tractor, don't forget to plug in your connectors...

Awesome suggestions guys (except the one above! No putput engine will be a good reminder). I will most definitely be putting in some time to install something on the tractor, and probably the mowers too.

 

If I leave a mower somewhere in a backyard out of sight to go grab lunch, I will shut the fuel off, release the break, pull a fuse, engage the blades and pull the key(thirty seconds of time). By the time someone figures out how to start it and finds a flat fuse to replace the one in my pocket if Im not back from picking up lunch or parts they deserve they mower.

I thought I was the only one that did things like that.

 

In the distant past...I would remove the coil wire...usually the biggest wire installed in the middle of the coil. Yes...it will still crank over but shall not start.
In my mind if you are there to steal the object and you are trying to start... it is turning over but does not start....I would leave ASAP. Very easy to do...just remove the wire and try to start... I am not sure but if you have a magneto instead of a distributor...you still remove the wire and it will not start. Ken

 

I went to a go-kart track once where they could remotely control your speed, im sure you could find a satellite powered style of this to remotely kill the engine, or put a gps chip in it, so you can track it....

 

Awesome suggestions guys (except the one above! No putput engine will be a good reminder). I will most definitely be putting in some time to install something on the tractor, and probably the mowers too.

I thought it was a simple alternative to accomplishing the same result as a switch...only the owner would know where to look to plug the wires back together...what's the difference between that and unplugging a coil wire which would be a lot more obvious...

 

Hey I did a couple things to my mower to protect it John Deere 820A interupt switch to the parking brake circuit so it wont crank. a switch to the seat sensor so that if they happen to find the parkig brake switch and get it running it will kill once they release the parking brake and another one tothe fuel selenoid so it will run out of gas after about 10 seconds.