TOPIC:

I have the Wookie Bible of electrical fault chasing. I'm going to get a multimeter now and I'll be hunting gremlins tonight. 

My current hypothesis is that the starter solenoid went bad. I was poking around near the battery and noticed that the terminal that attaches to the battery was badly corroded. I cleaned it up with a steel brush (wishful thinking), and put it back together. Didn't fix it. The body of the solenoid is pretty corroded as well. 

I tried jumping it from my car battery (car off), thinking that maybe just some extra voltage would fix the problem, but again, nada.

The battery is brand new (purchased, filled, and charged 3 days ago) so I'm working under the assumption that it is good. I will check the battery voltage as soon as I get home with the multimeter. The buzzing is still present from the main relay. Any attempt to start results in a clicking from the main relay. Will update everyone soon. Thanks for your help. 

I poor man’s backyard test for the battery is to have it mounted in the bike, fully charged. Turn on lights and watch batter voltage, once it drops below 12v shut everything off, disconnect the battery so there’s no parasitic, unknow draws. Watch the battery, if it’s good it will restore to 12.6 on it own within 10 minutes or so. Or take it to your local auto parts they can test it. I’ve see “new” batteries be old new stock, meaning it’s new to you be could be a couple years old. 

After picking up the multimeter last night, I took a handful of amateur measurements. Battery from terminal to terminal is happily in the 12.55-12.6 range. On attempting to crank (which again, only results in a ticking noise from the main relay), the voltage only drops by .05 instead of the .5 I would expect. Same story when measuring the negative and positive terminals of the solenoid. The solenoid reads at 12.52 or so, and will drop to 12.46-12.47 when trying to crank. 

I've got a hunch that the solenoid is bad - which is why insufficient voltage is making its way further down the system. In my bike (I'm unsure if this is universal among motorcycles), the lead from the positive end of the battery leads straight into the solenoid, where it is separated out and runs through the rest of the bike's electrical system. 

Some other electrical oddities to note: The main headlamp does not switch on, regardless if it is in the regular or high-beam position. This wasn't an issue about a month ago - when I last tried to crank the bike. The bike will attempt to 'start' when the headlamp switch is clicked forward, but not when it is switched downward. The tachometer needle will 'jump' up and then back down when the key is turned to the on position. This 'quirk' existed when I first picked the bike up. In order to crank the motor, the key had to be turned just enough to cause the tachometer needle to jump. In that position, you could crank the motor. Turn the key too far or not far enough and nothing would happen. I can still find the position in which the bike used to start, but as stated earlier pressing the start switch just results in clicking from the main relay. I mentioned this earlier in this thread, but once when I tried to start the bike a strange 'clicking' noise would emanate from the left-handed controls, and the bike wouldn't start. This went away after turning on the left turn signal and hasn't returned. All other lights seem to work correctly as of now (turn signals, caution). There is no horn installed on the bike - this is on my to-do list to fix. 

I will get a video of the current electrical weirdness of the bike when I get home later today. I've got a new solenoid on the way - hopefully, that will solve at least some of these problems. I will try Mikaw's battery test tonight as well. Although it might take a while considering my headlamp isn't functioning at the moment. 

Let me know if I'm on the right track, or am just jumping at what seems to be the easiest part to replace. 

If you look at page 20 of the guide there is a "step by step" test plan for a starter circuit, don't jump any steps and it will test the whole starter circuit
PS: if the starter was actually engaging the battery voltage will drop to approx 10-10.5v while the starter is cranking

Rather than looking too deep at all the other issues work through the starter circuit first (it may well lead you to the source of all your problems if it is a ground problem as I suspect) the key with electrics is to approach it in a logical and systematic way - even if the fault you have doesn't appear to be logical 

Eureka! (Kinda) 

Kicking myself - I found the electrical problem! The bike was on its center stand while I was trying to start it (D'oh). Took it off the center stand (after replacing the starter solenoid), and the bike cranks fine now. 

Filled it up with fresh gas, and cranked it up. 

The bike started with the choke in, and even settled into an idle after pushing the choke plunger back in. Letting it idle with my hand completely off the throttle resulted in it sputtering out - albeit very slowly. It started and ran well enough for me to take it for a short ride around the backyard, but it stalled and I walked it back. 

In my excitement, I went straight to the repair manual. I figured it was probably just a small adjustment that needed to be made for the bike to run as normal. I fiddled with the throttle cables to adjust their play - the manual suggests about an 1/8th inch of play and I had none. Started the bike - same scenario. Then I did something that might have been stupid -  I started fiddling with the idle adjustment screw. Just a half turn or so, but starting the bike after my adjustment resulted in worsened symptoms - the bike seemed less eager to start and would die more promptly. I've attached a video below of the current state of the bike (to the best I can tell I've put the idle screw back to where it was).

IMG_1743.MOV

There are some vacuum ports in the carbs that were left uncovered - the two that normally run to the air suction system were capped by the last owner, but the inner two are currently open (and have been since I've taken ownership of the bike). I'm thinking this could be part of the issue - too much air into the carbs leaning out the fuel mixture and resulting in the issues I am seeing. 

Below is the best image I can get: circled in red is one of the open vacuum ports, yellow is the one the previous owner capped. 
IMG_1745.jpg

Carbs were rebuilt following the Ness guide to a T, fresh seals everywhere. The previous problem of gasoline spilling from the airbox is no longer present. 

So,  a few updates. After some basic diagnostics, I determined I had run some vacuum lines wrong to and from the carburetors/petcock. I had the vacuum line for the petcock running to one of the fuel vents on the bottom of the carburetors. Pasted diagram below was very helpful for anyone reading back in the future. I had two black plastic tee's where marked below. I plugged the open vacuum ports, and ran one to the petcock. After that, the bike started almost right away. Still a nasty misfire down low. So I did a poor-mans spark test by pulling the spark boots to each spark plug and seeing what would happen. For cylinders 1 and 4 there was no change in the "idle". So, a spark problem. I realized then that plug numbers 1 and 4 both ran to the same ignition coil. After ordering a new coil from Z1 and installing it, the bike started right away and seemed to run smoothly. Leaving it to idle entirely on its own did result in the engine eventually bogging down and dying out, but it took a good 30 seconds before the motor would putter out. I've got a new (used) set of coil wires on the way, we'll see if they solve my idle issue. 

All that said, the bike started and ran well enough for me to take it around the neighborhood and some nearby back roads. The bike runs perfectly above 1100 rpm, pulls hard, and shifts well. The brakes stop well, and the thing sounds awesome. It seems to hold RPMs when pulling in the clutch to up-shift or come to a stop - might need some adjustment in the carburetor department. 

The next steps for me after the new plug wires are a rear diff fluid change and a new air filter. Are there any more general maintenance things I should be on the lookout for at this mileage (~26k miles)? Any recommendations for gear oil? What about gas? I haven't been able to find an owner's manual recommending an official octane - I've been using 90 ethanol free and it seems to work well on the bike. 

Changed the avatar, as the bike now moves on its own without a trailer.