____ Your follow-up post is appreciated Adam ! - (It seems I had
falsely jumped-to-conclusion on more than one aspect of your troubleshooting-case, and-so now your updated post-info conveniently curves me from still further
mis-speculation.)
____ Anyhow, firstly I must explain that I've edited your post only in that I've properly incorporated the
intended-use of the 'Quote' feature that's provided for visually separating our respective post-writings in the normally expected organized manor.
"
Between what my relatives told me and comparing the serial number to other posts pointed me to '67. "
____ Many '66-Scramblers with 6-didgit motor-numbers (such as
101234 weren't sold & titled until 1967, and-so were considered as 1967-models, although actually made in 1966.
____ Have you by any chance previously had the key-switch wiring completely disconnected and then later reconnected just according to what you've understood some-diagram seemingly indicating ?
"
****No, I left everything intact. The wiring in the headlamp looks pretty good so I left it alone. "
____ I had overlooked to include within my previous-posting that the picture of your key-switch's ign.circuit connections only included just
one green-wire ! ...
Ducati's (wire wasteful) wiring-scheme has one green-wire (that's connected to the yellow mag.stator-wire), which directly runs-up to the key-switch's ign.circuit
input-terminal,, at which point,
another length of green-wire runs-back from that very-same switch-terminal to the ign.coil's power/points-terminal.
So
one-half of that entire green-wire power-circuit seems to somehow be missing from your wiring-system,, and without the wiring-alteration you made to compensate for that shortcoming, the ign.spark indeed could-not have fired before, (meaning
just-before that wiring "rerouting" you did).
__ So this leads to the following questions...
Which-one of the two green power-wire/circuits is the
actual-one that's been disconnected from the k.switch-terminal,, the green-length from the mag.stator's yellow-wire, or, the green-length going-back to the ign.coil ??
How long has the ign.spark actually not been firing, (since the time when someone-
else must've messed-around with the green-wiring ?) ? _ (
I had previously assumed that you were simply troubleshooting an ign.system which had been working until a relatively recent malfunction befell it, but it's not a common-happenstance for such malfunction to develop due-to a length of wire coming-up missing from the wiring-system ! 
_ So I'm thus left to assume that you have taken-up where someone-else had left-off on an unfinished endeavor with the wiring-system. [?])
"
I did have to tie into the existing three wires from the magneto as they were in pretty bad shape. "
____ It's a common-problem for the insulation-jacket/coating of those original crummy/
crumby wire-leads to disintegrate.
"
I'd like to replace those three wires altogether but I'm hesitant to crack open the case. "
____ Unless you also have another reason to get inside there, it's just as well for you to leave those wires left undisturbed,, as they'll still continue performing their function well enough, (so long as left-be).
____ The green/kill-wire normally runs-back from the ign.switch's grounding-circuit to the ign.coil's mag.powered points-terminal,, and it need not be 'rerouted', but rather merely-just isolated in order for the defaultly-connected magneto-ign.system to be allowed to fire-up.
"
****I had referred to the electrical schematic for Scrambler 250 from e.n. 92712. It shows the green going from the block (opposite the yellow wire) up to the key switch, then returning to the HT Coil. "
____ Right, I'm sorry,, my quoted wording was fairly misleading, as it's that particular separate*green-length from the connector-block going up to the key-switch that I had previously overlooked & forgot-about and-also failed to fully contemplate and include mention of, (due-to the absence of the second green-wire in your key-switch pic) !
__ (*
That extra length of green-wire to the key-switch was pretty-much unnecessary for Ducati to have included, as only one length going the headlamp-route [between the ign.coil & k.switch] is actually required !)
This Ducati-circuit oddity has already been covered a couple times before in old threads concerning stock '66-Scr & 160-M.Jr electrical-schemes, and I also then certainly made-point that the primary green-wire should rather be left yellow-colored and
rather directly-connected to the ign.coil (for all the obvious functional reasons) ! _ And it seems you've also realized the good-sense of this simple circuit-mod on your-own, as well.
"
I simply took it from the block to the coil keeping the return intact. I'll post the schematic that shows this. "
____ I see from your drawing-modifications to the stock scheme-diagram that you've indeed simply jump-connected the stator's yellow-wire (with your added
ghost-green jumper-line) to the power/points-terminal of the ign.coil ! _ And that's exactly how Ducati should've done it in the first-place, so as to simplify the wiring-scheme and current-pathway (and-also save a length of green-wire) !
So now your green-length which you've left intact, can be left connected between the ign.coil & key-switch and function as the '
kill-wire' like I had expected.
__ Anyhow, since your key/ign.switch wiring connections are now pictured hooked-up correctly, and the switch itself is apparently not a valid suspect,, please follow-up with what you now think might still be wrong with whatever may be the actual cause of your presented concern.
"
Take a look at the schematic I've posted. I colored it
While connected originally, I would not get any spark with key pushed in. Once the switch was removed from the equation, I got spark right away. "
____ I see that besides coloring the pertinent green-wiring,, you've also left a length of it not-only uncolored, but also
Xed-out as well ! _ What's the reason for that, exactly ? _ Is yours missing, or what ?
If missing, then that's got to be compensated for,, or-else guess-what, there can't be any mag.power conducted to the ign.coil !
Or maybe rather, perhaps you (elaborately) pulled-out the missing green-wire from out-of the headlamp-harness and-then rather directly-connected -('rerouted') it straight-to the ign.coil ?
I guess that could explain your posted specific scheme-changes indicated for your altered green circuit-pathway,, AND-also, likely explain why your key-switch pictures don't include showing the missing green-wire !?
____ I'm wondering exactly what-
all you've since altered (intentionally or not) from how everything
was "
connected originally",, that your Duke hadn't before possessed any spark, back-
then !? _ In other-words, if you were to reverse everything you've done, one change at a time,, would your previous ign.issue ever come-back, or not ? _ I wonder about such because your ignition-issue shouldn't have developed all on it's-own, and-also shouldn't be so simply fixed by merely-just "rerouting" the green/power-wire & it's
connection away-from the k.switch-terminal and-to the ign.coil, (without something-else being changed as well) !
Was it yourself, or someone-else previously,, who apparently altered some of the factory green-wiring, (as is indicated by your
Xed-out green-length) ?
__
I'm thinking that it really wasn't actually the removal of the
key-switch from the circuitry that seemingly changed your results,
but rather that the magneto-power of the yellow/green-circuit wasn't properly getting normally circuited up-to the k.switch in the first-place (so that the mag.power could then continue-onward back-to the ign.coil) !
"
I cleaned the terminals of the switch this evening. "
____ If you also included the switch connector-tabs and your effort was actually fruitful, then expect no-more than .1-ohm between it's contacts.
"
If that doesn't work, then I'll run a new green wire to the switch. ____
That would
more-likely result with providing the desired effect ! _ However, as should be obvious,, you really only need just one green-wire/circuit (to connect between the ign.coil & k.switch) !
So I suggest that you merely just retain your jumper-wire/connection between the yellow/power-wire & ign.coil, (and-also of-course continue with the stock employment of the single green-wire/circuit from the ign.coil to the [properly grounded] k.switch ground-circuit).
That way, you then
certainly won't have-to
depend on the apparently missing green-wire/power-circuit (that's
UNnecessarily detoured up-into the headlamp before continuing-on back-to the ign.coil) !
As it seems at this-point, that it's
that (presently inexplicably)- failed green-circuit which has prevented your ign.system from powering-up.
Hopeful-Cheers,
DCT-Bob
Apparently having not realized that their Duke's ign.system was-not meant to be run with the battery.) 