So where is a good place to get a voltage reading away from the battery terminals? I remember seeing aux power cables on one of the wiring diagrams...
As you are fully aware, i am only an idiot n00b and have absolutely no idea what i am talking about, but i *do
* have the highest percentage of plain old dumb luck statically charged into my being from rubbing my pant legs up against so many car doors every day while lane splitting, so with that said, and with it given that my bike is an '87 California model . . .
Two places i can think of that should be checked and are pretty easy to check are the red terminals on each of the ignition coil primaries. The ignition coils have two little tabs on them that booted wires hook up to, and they have two spark plug cables running out of the the side. If those are low voltage then the fire in the spark plugs is going to be likewise lower, and that is true as a formula as long as the coils are good ( no shorts inside themselves between their windings ). The front cylinder's ignition coil is under the front left neck-shield over the left front ear ( remember that screw i was talking about that fell between the frame and the radiator? yeah, keep your fingers on those as they come out.
). And the rear's ignition coil is on the front side of the battery box. Both measurements are on the left side of the bike. You should also test with three different grounds ( or more ). For example, sticking the meter probe into the back of the connector's jacket for the positive side of either coil frees up one of your hands, but also keeps that connection "steady" as it can be. The rubber holds the probe in place ( presuming your connecting boots are like mine which as you know could be totally different even though nothing on this bike has ever changed over the years
). In any case, after your probe is solid on one of the coils, use the other probe to first, the frame, then the crankcase itself, and then the battery negative terminal. These are the three major grounds on the bike ( battery box excluded ). Several parts rely on the frame to be ground ( for example, the fan switch has one wire feeding it ). And there is a big black wire from the crankcase to the battery box on the right side where the battery box bolts onto the frame. This is ( electrically speaking ) the "common ground" even though the Kawi electrical engineers in their infinite wisdom chose to run the negative battery terminal some place else ( disregarding every design principle ever penned and giving people like Slim good valid reasons to "lean toward the ground" ). Regardless of where you make those measurements for ground, your voltage to either coil should be the same. To clarify, if you, for example, have the red probe on the rear coil's red wire, you should see the same reading for voltage regardless of which of the three ( or more ) grounds you choose. If there is a difference beyond a tenth of a volt, then you have what is known as a "voltage drop" between those two points of ground. If there is NO voltage or a huge difference in your voltage at any two grounds, then you have a "broken connection" which simply means one of your grounds is no longer hooked up mechanically enough to pass electricity ( could be corrosion, loose, disconnected, have some kind of junk that found its way there by somebody's kludge like a rubber washer, etc. ). On paper, and ideally, the readings should be exactly the same. Another reading to check is that both of your coils should be the same voltage as well. So if you are reading, let's say, 13.2 volts on the front coil using one particular ground, that same ground point should result in you reading 13.2 volts on the rear coil as well. If they are different then you probably have a short, or a near short, or a leaky capacitive or resistive short in your harness or in, around, or near the connectors to your ignitor box. The ignitor box is that fairly large black square box with the square rubber hood surrounding its two molex connector sockets on the right rear lower side of the battery box. If either of your coil primaries are shorted, then you will also get a different voltage reading on that second test. It wouldn't necessarily mean that the coil was no longer useful, it would only mean that a section inside had lost its insulation between two or more windings. On the presumption that at least ONE of your coils is "good", you could test them in two different ways. 1) by swapping them one with the other 2) by measuring the resistance in each of them ( which should be approximately the same ).
Hope this helps, and please remember, i am only chiming in because the experts have yet to find the time, so for now, please accept some of my dumb luck advice.