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Join Date: Nov 2007
Location: Chandler, Arizona
I would get rid of those switches anyway, they are known to corrode and fail on all bikes. I remove them from all my bikes after having a couple fail out on the road. They serve no purpose for an experienced rider. But I don't believe they are the problem in your case, because if they were bad (either one or both) the engine would die at any speed, not just idle. An air leak is possible, but unlikely if it runs good other than at idle. To check and make sure, start the bike and let it idle until it gets hot (the fan will come on) then take an unlit propane torch with the valve about halfway open, and hold it around the carbs and manifold. If there is the slightest air leak, it will suck in the propane and the idle speed will go way up fast.
I suspect it is a problem with some part of the idle circuit, or, the throttle and or cables could be sticking slightly. You may have the idle set to low, but the throttle is not quite closing some of the time, so it keeps idling. Once in a while it will close all the way, letting the idle speed drop too low. I have encountered that on more than one bike. Thoroughly lubricate the throttle assembly, the cables, and the linkage on the carbs. The throttle should snap back hard when released, with no binding of any kind. You should easily be able to hear it snap closed. Then you can set the idle speed.
Not suggesting you do this, But I removed the "push" cable on mine, the one that connects to the back on the bottom of the throttle housing. Now when the throttle is moved, only one cable has to move in it's housing. It resulted in much smoother throttle feel, the "pull" cable opens the throttle, and the spring on the carb closes it. If the cable breaks, the spring should immediately close the throttle. If the cable breaks and binds in the housing (which could happen with two cables just as easily) the kill switch is just under your left thumb.
I am a motorcyclist, NOT a biker.
1997 Vulcan 750, purchased about a week ago
2006 Sportster 1200 Low
2013 Royal Enfield Bullet 500, converted to carb
2001 Yamaha XT225, heavily modified
2004 Honda Rebel 250
1979 Vespa P200E
2002 Vulcan 750 parts bike
1994 Yamaha XT225 parts bike