this is going to sound real stupid but I'll try and check your switch just unplug it and see if the bike start with the power switch un pluged.....
if the bike starts up fine with the kill switch unplugged then what has happened is you got water in the switch or the cheap switch broke.
the switch on my bike stops working every single time it gets water in it, and the exact same thing happens it'll just cut off and die, and I will not be able to start it again until I will go and play with the switch or disconnect it. finally I did away with the switch all together and installed a real one, I had to do that because the vibration from the bike was causing the switch to vibrate around and cut the bike off and on while I was driving.
when your bike cuts off while driving the first thing you should check the switch in order to check it all you have to do is disconnected and see if the bike starts back up if it does and the swhich is the problem.
if the switch is fine then you can move on to the spark plug boot in the magneto. it has been my experience that the CDI box hardly ever fails I am still on my first CD I am on my second engine it has over 4000 miles on it and it still in perfect workingorder