We keep heading (I keep going) down a path that will likely contain some wrong information or at the least misleading information sooner or later. Hell..I'm wrong enough of the time when I think I know what I'm doing..let alone when I know I don't.
Using the web anytime on the weekends stinks, Sunday evening usually the worst..have been trying to get to
http://www.buykawasaki.com with no luck the web is so balled up. Go there, look up your bike, see what you can find for wiring information.
No warranties expressed or implied, everything said applies to the'H'. To Your bike? Don't know:
The yellow wire is probably the hot from the lighting coil. It will be AC, as it's the product of a magnet spinning around a coil..and that AC will be unregulated. Speaking of which...where is your regulator? Do you have one? In the 'H' it's under the seat, bolted to the frame. It differs from the spark box in that it will have only two wires going to it...hot in, regulated AC out.
If the yellow wire is either disconnected or
not connected to the regulator or load,
you will see voltages approaching 100VAC as engine RPM increases. Bikes a bit older'n yours sometimes had no regulator at all..the system depended on lighting filaments for their 'regulation'.
If you have a regulator, it will be wired after the (missing) switch. When the switch is made, lighting coil output is connected to the regulator and the lights (or whatever load..I run grip heat 'fer instance). It is an AC regulator, and it will be around 13VAC depending on your light load, your light coil, and primarily the engine RPM.
OEM lighting coils are good for about 45 watts. The OEM headlight and taillight have it about maxed out.
Note the regulator not being switched into the circuit until the light switch is 'on'. That is of particular note when you are wiring up a new shell, or troubleshooting the lighting system. DO NOT FAIL to include the regulator when you are testing your lights or wiring. Ex: You loosen the shell from the clamps so you can get to the backside of it, disconnect the wiring headed toward the back of the bike for more clearance. To 'simply' find out if your lights work, you connect one side of the lamp to ground, the other side to the switch load tang. Start'er up. Hit the switch. Great! The light works! You blip the throttle to see how bright it gets....
...and it does get real bright...for a split second..and then it blows.
Why? 'Cuz you left out the wire going to the regulator.
Remember you are switching the regulator in AFTER the switch..it is in parallel with the lights!
One more time...all of the above applies to the 'H' model KDX.