My weed eater has a kill switch on it. Can someone please explain how can I hook this up to my third channel? If that's not possible then I suppose I could always hook up a servo to the choke.

Any thoughts?

You don't need that weedeater kill switch.Just back off or take out the idle screw and adjust your idle with your radio and when you need to to shut the engine off, just push forward with your finger (if using a pistol radio) and it will close the throttle butterfly all the way and shut it down.If you are running on the bench and need to shut it down just put your finger over the carb hole and it will stop.I set mine up this way ,but also use a failsafe in the radio box that will shut down the engine,by setting the failsafe to the throttle servo,which will close the butterfly and either shut it down or at an idle if you have a clutch.This is if your radio looses contact with the receiver,either because of out of range,other loss of signal or low battery power.Just remember to turn your transmitter on first before the receiver and to turn it off last last after turning off the receiver power.On first,off last.
Another thing,take out that choke butterfly and rod and plug the holes where it was with quick setting JB Weld (6 min).You then choke the carb with your finger.

Cool thanks. So the idea is that the servo will close down the carb when the tension on the cable is released. I figure removing the butterfly allows for more and better air flow.