Sneezles you are correct lucky us having RT and MarkT the dynamic duo. 

Much to my frustration,and as others have stated,yes they bloodywell are.I have been through as many as four before i got an NOS one from Gr8 Uncle Al for my RT1. Will the Lambi ones not fit? I would say that you have more chance of getting a good one from the scooter network,or as RT pointed out ,and Mark T at the time, mount a Honda one next to the coil thus removing the faffery of pissing about putting one in place on the stator plate.
Most ancient ignition parts you find in the UK have been subject to damp storage no matter where you get them.

Take it easy guys, i'm know what i know but am sure capable of making mistakes.
In some cases [lots] i'm happy to be guided by MarkT & others.
Unless i'm sure i'm right haha then i dig my toes in--so even look sillier if then proved wrong. Thanks.

MarkT point(s) well taken about digital meters not being able stabilize at low readings.

I mentioned my prior experience restoring Lambrettas which all came from the factory with 6v points ignitions in a number of different flavors including 4 pole and 6 pole stators by Marelli, Filso, Motoplat, etc., and for 26 years our tried and true tool was this little "buzzbox":



Because it gave an audio signal when the points opened it was dead accurate because you could put your flywheel at your timing mark (usually 23° BTDC) and then adjust the point gap by moving the base plate with the set screw loosened just slightly until the unit beeped. No need to go all crosseyed trying to look at two things at once, just listen for the beep. The other great thing about this little unit is that the beep and the coinciding little red light only work if your points are working correctly. If there's an open or a short, you get either nothing or an always on situation. For this reason alone I never paid any attention to ohms readings in the 26 years I dabbled with those little bastards.

(All Lambrettas all had slotted stator base plate holes too, allowing for even finer tuning should your desired timing setting not fall within the desired .014-.018" points gap when open. With the Yamaha's fixed stator base the only way to affect timing is to change the points gap, which I find odd, but I digress....)

RT I watched your videos and I will be grabbing my trusty old analog Sears automotive diagnostic box that should be able to give me similar readings. If the Yammy wasn't the only remaining points operated machine in my stable I'd buy another buzzbox in an instant.

In short(s), timing is a moot point(s) if there's no spark, haha!

If you buy another "buzz box", don't get that exact one.  That model is more for Kettering (battery powered) points ignitions.  You might hear a tone change slightly when the magneto points open but it won't show a distinct on-off like a true magneto points tester will. 

(Aircraft magneto testers are the best I've found still available in modern times...  they sense the change in inductance and are not just simple continuity testers. www.aircraftspruce.com/catalog/topages/s...ronizer_12-16903.php)

I believe the way Yamaha has designed some of the magnetos pretty much insures you can't mess up the internal timing with a set of bad points or something by not letting you move the plate to compensate.  Why?  Magnetos also have "internal" timing...  the points need to open very near the point where the voltage created by the spinning magnets has peaked in the source coil.  (You can feel this position as the "bump" where the magnets most strongly influence turning the crank...  the "bump" can be annoying sometimes when setting timing because it gets harder to turn and then "jumps" forward right at the timing point...)  This "internal" timing is critical because the window of when the points can open in relation to position of the spinning magnets is very small for good spark. 

 

I beg to differ on that buzz box not working with magneto systems but with battery powered points systems. I used one thousands of times over the years with magneto systems, and it was dead accurate. It must be engineered to trigger the light and tone at that jump from full continuity to the 1-2ohm range you mentioned previously. In fact it wouldn't make sense to use it with a battery points system because in that situation a simple test light would do the trick since the points are not wired to a source coil and the points go from full continuity closed to 0 continuity open.

Tomorrow I will do a test with my trusty old Sears Engine Analyzer, which has an analog ohms function that should be able to tell me if I'm seeing the 1-2ohms with the points open, and I will report back what I find.

I didn't say it would not work.  That exact model in the picture you posted is one I've seen for sale lately is the type that changes tone slightly when points open.   HVC cycle is one place that sells them. 

Still works but is not as nice as the type that is silent with points closed and only makes sound when point just open like the aircraft tester I linked and some of the vintage testers did. 

(I find the constant buzz-tone change type very annoying...  personal preference.)

Actually, I need to correct something.  I don't know if that model will change tone when points open..  I never got that far.  I returned it because it's simply a "continuity buzzer" that makes noise when you connect the wires together or the points close.  (not open)

And it is designed for battery ignitions which as you said is not needed.  Simple test light works. 

Just trying to save someone from buying a tool that is not what it seems to be. 

OK, found the issue with both the original misfire and the current lack of spark. The inner end of the source coil winding (the a shorter wire with black insulation on the far right in the photo) was not connected to anything. As you can see it's twisted on the end like it had been wrapped around another wire. I would think it should be grounded, or possibly connected to the charge/lighting coil wiring, perhaps the yellow? The manual doesn't show this much detail and I looked around quite a bit on the interwebs before coming here to beg for answers. The outer end of the winding is much longer and has brown insulation and connects to the points, condensor, and black/white wire in the loom. I assume this is correct, yes?

I'd say you're right onto it. Has to be earthed for sure.
Had to look back to see what bike ya talking, but in the early days they earthed the source to within the lighting coil [not sure i understood how that worked].
But i remember earthing the source separate as a get me by measure on a DT1 when the lighting coil had come loose on its post & causing an ignition missfire & worse.
I didn't know they still did that these days "78 but it wouldn't be earthed to the yellow which is the lighting output highest voltage, but is there an odd spare wire from within the lighting coil--looking like it came from 'there'?.
I'm not sure anymore but if you earth it to the post with a screw terminal, or anywhere convenient it'll earth really & should be away. Be good to hear comments on 'that' earthing into the lighting coil.
I think someone said once it boost spark at high revs. food for thought. Let's know how it pans out.