The only way I would have a Kill switch on my china engine is a toggle switch or a key switch to cut the blue wire not unlike how they would do it in let's say... a car. Grounding the white wire in my experience is asking for magneto failure. That white wire is for accessories anyway like headlights.
I deal with cutting off my engine by simply twisting my throttle back. I set my idle to stop my engine when the throttle is down.

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