Thanks for all the feedback. I understand "is good" raises an eyebrow when we don't know one another. The bike won't start right now, these tests are with a charged battery (reads 13.1v with the ignition off) cranking in neutral where appropriate. I didn't note what the RPM when cranking is, but it sounds normal.
In order of questions:
The output from the exciter coil is currently 37v AC measured at the plug near the CDI. I seem to remember it was 42V last winter when I checked but I can't find where/if I recorded the exact value (I just noted it was "ok"). I went through EVERYTHING last winter trying to nail this, and just forced its intermittentness undercover so I thought it was solved or maybe a loose terminal or something, then damn near had to rent a trailer to get the thing home from the city... I kept some of those measurements but not all. Likewise I noted last winter that the exciter coil resistance checked out as ok, but didn't record in my maintenance log what that was. This evening I'm seeing 200 ohms with the ratshack analog meter and 280 with my Flukes. They say a man with one watch knows what time it is, a man with TWO watches is never quite sure. I trust the Fluke more except in places where the higher current of the analog matters (like the CDI itself). Both those values are a bit over the spec of 100-200 ohms.
I can't test the exciter oil output when running because it won't run at the moment.
This thread (https://advrider.com/f/threads/klr65...-query.738488/
) offers *cranking* values between 30v and 60v ac (pretty big range!). I have no baseline for the measurement on this bike prior to this issue (never had reason to measure it that I can recall). Interested in input.
The wires from the stator show no visible damage inside the case nor out, but that's one of the definite possibilities. I have a pic of the stator itself I can post (from last winter) but it looks like others I've seen. It didn't occur to me to meter from the presumably bare wire exiting the stator windings inside the case to the terminal end of the wire for resistance. I will certainly do so the next time I have the case open.
Compression: 70-90 with KACR intact, 160-190 with the KACR disabled with a little stub of hose in the works. Those numbers are on a cold engine that hasn't been started for a while and hasn't had oil squirted in or anything; range is because I'd borrowed an additional tester to verify I wasn't using a lousy meter. The bike has around 15k on a fresh 685 and it doesn't live a super hard life anymore... the 685 took it from an oil guzzler to using almost nothing from one change to the next. My chinese static leakdown tester crapped the bed so I can't apply that, but those numbers seem very fine for a 650/685 to me.
With the plug cap removed from the wire I can see a spark jump a 3mm gap to bare metal on the engine. I used a caliper to measure that gap as best I could (tried to brace my hand so the gap wouldn't change while I measured with the caliper after releasing the button). Again, I've never tried that test before so? This is in a dim garage, easy to see what spark there is. Interestingly spark looks bluer this way than across a grounded plug.
I can crank the bike with my thumb held squarely over the end of the bare high tension wire. I can definitely feel the juice, but it isn't painful. I would say I am no more than average on the pain threshold, though I do work with electricity so the sensation of getting "bit" is not as new as I wish. This seems very vague, though, since the path to ground is presumably through my other hand on a rubber grip pushing a plastic button, no? Kind of why I got that metered spark tester gizmo--to remove the estimation.
Battery connections (+ and -) are good and clean. I don't think I've EVER disturbed the negative lead where it connects to the motor near the starter though. The ground up near the steering head is also tight and clean. Part of why I want to jump the CDI into a running state is to cross all that off: With an old CDI ignition like this, as long as the rotor is spinning past the stator and the wires between to the CDI then to coil and plug are solid, the only that's relevant is the CDI back to the block. It seems possible that somewhere in its path through the key and through the kill switch there could be either a lousy connection OR a worn insulation allowing a slight leakage to ground.
Coil is checked and very near spec AND I recently bought a second used coil which also checks to near spec. The resistance on the primary coil is so tiny (.15 to .21 ohms per Clymer) that it's awfully hard to really get good resolution, but it's not shorted nor open for sure:
Original coil .1 (fluke) and .2 (analog ratshack); eBay coil .1 (fluke) and .25 (analog ratshack)
Original secondary with wire 3200, eBay secondary w wire 4450 (spec is 3800-5800)
Original plug cap 4000, eBay plug cap 4600 (Clymer references 5,500 as an unofficial number but says Kawi didn't offer one)
On top of that, last winter I borrowed a known good coil complete through the plug cap off my father's bike (they live 700 miles away but were visiting) and that did not cause the bike to roar to life.
I'm interested in input on any of this and any more guidance. I'm going to try to jump the coils directly to the CDI and make a temporary CDI ground if I can confidently get that much crap into the terminal block without risk of a short. I really need to actually find and resolve this problem; with the way I rely on the bike now, getting it running again won't be acceptable if there's the risk this will recur. I thought I had it licked last spring and it damn near got me fired over the summer.