Right, ok me not thinking or reading all the story.
So we need kick start revs? to get startup voltage--of course haha.
I'll try again tomorrow.
I might try my peak meter as well but i guess that just doubles the voltage.

RT325, you did fine!  That was probably at least cranking speed which is much more than 50 rpm.

(RapidRob says he's turning it at 50 RPM, which is slow and could account for low voltage)

To Rapidrob: The Fluke 87 has both a Min/Max and a "Peak" Min/Max setting. The base min/max setting records at 100ms update time (too slow to see the spike) The "Peak" setting records at 1ms, fast enough to see the spikes. Your picture of your Fluke (earlier in this thread) showed it to be recording at 100ms, not Peak. As for measuring the source coil output with the points open, this basically just confirms the ohm readings, the coil windings are not directly shorted nor open. It does not test the integrity of the insulation on the windings. With the points held open, the coil will produce a sine wave at varying voltage and frequency directly proportion to the rpm, just like a lighting coil.(perhaps slightly distorted since the condenser is still connected) The peak value of this sine wave (negative & positive) is nowhere near the voltage produced by the collapsing magnetic field as the points open. This is how the energy transfer magneto works. It's this spike that can find it's way thru a weak spot in the insulation, instead of passing to the primary of the ignition coil.

RT325 tried it but never got spark to jump the plug but gets to the wire just isnt powerfull enough

Alnarv,

Ignition coil is a simple AC transformer as you know.  The high voltage secondary output is created by a sudden change of magnetic field in the primary ignition coil windings.  In a common Kettering (battery points) ignition, the points closed creates a magnetic field in the ignition coil primary winding. The points opening suddenly collapses the primary magnetic field and Spark!

In the Yamaha Energy-Transfer magneto (aka "mechanical CDI") the ignition coil primary winding has no magnetic field at all with points closed.  The magnets and source coil have been carefully timed so that the sine wave is at or near peak when the points open.  Points opening allows this voltage to create (not collapse) a magnetic field in the ignition coil primary winding.  This sudden creation of the primary magnetic field results in the high voltage in the secondary and again, Spark!

I also have to say that RT325's blocking of the points open verifies an AC primary RMS voltage reading without a scope or $600 multimeter and the knowledge to use them properly.  You might be correct that is won't load the coil enough and reveal a defect...  but it is still a valuable and brilliant test in my opinion.

(The fact is cranking without the plug experiencing the added load of compression and fuel under combustion conditions might not reveal a source winding flaw either... just like sometimes a plug will spark fine when removed but won't spark when installed.)

#34 not always the coils fault although sounds like you need one due to plug lead length. Try shutting the plug gap down to almost zero & look in the dark. How do you determine its getting there but not producing. Maybe take this problem back to your other separate post to avoid complicating things. All good though. Hope you have a clean plug or even trap the lead to a fin & should jump to the fin.

Another thread hijack in response to post 34...  NGK makes a spark plug wire splicer that I've used to repair a damaged wire in a pinch...  friend still has one on their generator from years ago. 

Here's an aftermarket kit with wire and two splicers (only need one)  ebay splice kit

Here's just the NGK splice.  Ebay NGK plug wire splice

Try again, just because. Might be of use to someone as is from a running system--poor old bike.
First short vid is kicking it over through compression with points bridged & unhooked from the plug coil
Goes to close to 15AC volts with a good kick. 175cc lots of comp.
youtube.com/shorts/MyJ_KtM3DwY
Second is of having it plugged into plug coil.
Still had points bridged & not sure now if plug lead was off or on the plug but think it was off.
Got up to close to 7AC volts

Third vid is of it running till carb fuel ran out but this time using a peak voltage meter set on 500 volts & went to about 100 "peak" volts. Other two tests were on just AC volts on the AC scale on the old Yamy meter.

Hope they play but might play on their side. I see first one is only via the link think because its a short vid but still plays.

Markt: I agree with almost everything you said above. Except the part about the voltage from the source coil. As RT325 showed in his experiment, the coil develops about 15VAC at kick speed (that is an RMS measurement of the voltage) The peak of that sine wave can be calculated to be approx. 21volts, nowhere near enough to develop a spark voltage in the ignition coil. ( all the early Yamaha manuals state in the "how it functions" section say the source coil sends 150-300 volts to the primary of the ignition coil which steps it up at 50:1) The 150-300 volts comes from interrupting the flow of current to ground in the source coil when the points open, which causes a collapse of its own magnetic field, thus sending a very short voltage spike to the primary of the ignition coil. This actually helps explain why dirty points cause a lack of spark, if the points don't send the coil current to ground, the primary of the ignition coil will only see the 21 or so volts peak from the source coil sine wave. I suspect that in RT325's last video, the analog meter may not be seeing the absolute peak voltage, or the engine only needs 5000 volts to spark. (100 volts from the source coil stepped up 50 times)

Thank you to all who have replied! The vids show exactly what I'm seeing TURNING the engine over with a drill motor...plugs out....oil in cylinder
16 VAC out of the source coil. That using the Fluke 87 and the Simpson 260 meters.
What I have not done is pull the head off of the engine and try to mount a dial indicator.
It very well may be the points are no where near where they should be when opening. ( .015 gap )
I've got to figure out how to mount a dial indicator holder onto an aluminum cylinder? Hot melt glue?
I have the angled two plug head.