I just built a non-kit cruiser build with a minibike engine, using an ht kit throttle grip to an external throttle linkage (not that that matters). I wanted a clean build, so I used the killswitch built into the kit throttle. The engine had its own killswitch, but it was attached to the engine and I needed the switch on the handlebars in case of emergency. I disconnected the engine's built in killswitch from the ignition and attached a wire from the kit switch. I grounded the other wire from the kit switch to the engine, and it works just fine. Been running it since I built the bike almost 3 months ago. You can use a light switch if you want, but it wont look too nice and will probably be difficult to mount on the bars, which is really where the killswitch should be in case of emergency. Order a kit throttle setup with a killswitch built in and you'll have a perfectly safe and clean looking killswitch.