Kill Switch Won't Work When The Engine Runs Aaway

yuckfoo

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My kill switch always works. Except in one situation where I really need it to work. My engine is running better now but I still had one instance today where the engine revved really high with the clutch held in. Using the kill switch didn't work, closing the choke didn't work. I had to hold the brake and let the clutch fly to kill the engine. What would cause the kill switch to behave in this way?
 

Greg58

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Double check the carb, intake and cylinder base gaskets for leaks, that sounds like an air leak to me.
 

yuckfoo

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Double check the carb, intake and cylinder base gaskets for leaks, that sounds like an air leak to me.
Yeah, everyone keeps saying air leak. But I can't find one. And the bike was actually running ok for the first time. It was only once that it revved up on it's own.
 

Greg58

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If it revs without the throttle open that's a sign it's getting air somewhere, check the case gasket where the two half's go together and the seal on each side of the crankshaft. The seal behind the magnet is thinner than the one behind the small gear, the mag side is the one I've had trouble with.
 

yuckfoo

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Most likely the throttle cable end jumped out of the socket and held it open.
I saw a video today about a two stroke motorcycle engine that was doing the same thing. Apparently it was getting too hot due to an air leak and was dieseling. I need to learn how to check the crank seals for leaks. I have zero idea how to do that. People just say "behind the magneto" and "behind the clutch cover" but I don't see anything there. Is there a video somewhere or a post somewhere that describes how to do this? I've checked the intake (both ends) head gasket and base gasket multiple times. No leaks that I could find.
 

Sidewinder Jerry

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The kill switch not always working would have nothing to do directly with an air leak in the carburetor. In directly the high rev could be causing increased frame vibration which in turn could be causing loss of the ground contact to the kill switch.

Here's how I fixed the issue when it happened to me. I used a self tapping screw through the clamp and into the handlebar. This served two purposes.
It fixed the grounding issue and helped keep the switch held in one place.
 

Sidewinder Jerry

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