If you are using a Fluke 87, you can measure the very brief voltage spike when the points open. You have to set it to read peak min/max, max, and 1ms update. That is fast enough to see the spike. You should see 200+ volts (only lasts 2-3ms) The reason Markt wanted to know the points closed resistance is that if the source coil current is not grounded completely until the points open, it will not produce that spike.

ALNARV thanks for the 200 volts from the source coil. I'm only seeing 16.I pulled the flywheel off and tried to determine how strong the magnets are. They will hold the weight of a 1" box-end wrench. While not super strong, needing to have to pry things off of the magnets, there is still a pretty good pull.I measured the coil / points again and got the same readings.with the points CLOSED I'm reading 0 ( zero ) Ohms. This is all the way up to the Ignition coil primary input. 
Wrench on magnets
i.imgur.com/0VT3wsz.jpg

Points Closed
i.imgur.com/sEPR4kC.jpg

Points Open
i.imgur.com/Iy1gxIN.jpg

Ignition Coil Secondary ( High Voltage )
i.imgur.com/DB0yyVa.jpg

Close up of Secondary winding
i.imgur.com/QGgEpRi.jpg

IF the Source Coil under the flywheel is supposed to be producing 200 volts at Kick-started RPM's, the coil is bad.
It is only producing 16 VAC at 50 RPM ( electric Drill motor )

 

I pulled the Source Coil out of the frame and read through it using a digital and analog meter.
i.imgur.com/1yM0sRl.jpg

i.imgur.com/tsFf18r.jpg

Reading through the ignition coil
i.imgur.com/WrRkCgI.jpg

Backing plate ground
i.imgur.com/Ac1jraf.jpg

Reading through the coil, same reading through wiring as well.
i.imgur.com/JsgD8CD.jpg

Voltage at spark plug lead. 300 @ 50 RPM
i.imgur.com/8xsO5a4.jpg

I extrapolated the 16 Volts input and 300 volts output at the Ignition Coil to 200 volts input and get over 3,700 volts output, more than enough to produce a spark.
I'm leaning towards the Source Coil is bad / weak.
I may replace the Condenser as well for no other reason than I cannot be sure it is still good. It does charge  / discharge.
What do you guys think I should replace / troubleshoot next?
I'm the 4TH owner of this bike, the last 3 could not get the engine to spark and gave up.

50 RPM is way low for cranking speed. 

 

I would buy Yamaha or Daikhi points and condenser also did you check your plug cap they do have a resistor inside what are you using for your spark plug.I’ve never had a source or primary coil go bad. My fingers are crossed that I didn’t jinx myself. 
 Ps You can send it to DEET and he can fix it 

Also looks like you have meter on max and 100 ms?  That's much longer than the spark duration the setting Alnarv said to use. I can't say much more because voltage output testing is not something I've ever done and got a good reading with a multimeter.  I don't have a Fluke 87 either.  I do have a few oscilloscopes and my memory says peak was over 100 volts for spark but I'm not sure I saw over 200 volts on the scope. 

Are you using an original Yamaha ignition coil?  Dozens of people have had brand new aftermarket coils installed that might read the correct ohms but simply will not spark.  Several times here someone has replaced the original coil with one from ebay, then found and fixed the REAL problem...  still no spark...  until they put the original ignition coil back on or got a known good replacement.  SPARK!

I think you said you had a lot of bikes?  I've found these ignitions to be pretty tolerant of different points magneto coils...  maybe try your coil on a running points mag bike or try a known good ignition coil from a running bike? 

I should also say the absolute minimum "accepted" voltage for a reliable spark in a running engine is around 10,000 volts.  And that's extremely marginal.  15,000 +/- is likely what a decent points mag will produce. 

You'll get a spark with 3700 volts in dry air and a narrow gap but it probably won't be good enough to run when you add fuel and compression.. 

It really does sound like you fixed the basics and if you have a good solid ground connection with points closed and with around 2 ohms with points open usually you'll get a spark with a good ignition coil.  I can't remember ever not having a spark on a 175 once those two parameters were met... 

I harp on the reading with points closed because several times I've been told points are clean (or new) and they send me the ignition or bring the bike over and a simple proper points cleaning is all it needs...  brand new points often develop a thin film of non-conductive film that needs to be removed with some electrical contact cleaner and strips of card stock. 

Bad condenser unless shorted to ground which yours can't be from what you said, can create a miss...  but it will spark without a condenser at all. 

I agree with everything Markt said above. First, you have to hit min/max, then peak min/max to get the meter to read at 1ms, then check the output at the black lead going to the ignition coil primary. (you could also use an ocilloscope to see the same thing) A resistance test of the source coil can only tell if the coil is either open/shorted or not. While extremely rare, the coil can go bad by having the insulation on the wire break down, allowing the voltage spike to jump between windings instead of going to the output. I had this on my CT2 and there should be a thread covering this stored somewhere on the site. The only way to detect this problem is either in service test or use of a high voltage motor winding testor like a megger or a hi-pot. After I replaced the source coil on my CT2, I unwound the old coil and found the bad spot in the windings. It had tested completely normal using an ohmmeter.

Alnarv, you did have spark and the bike ran with the deteriorated stator coil if I remember correctly?  It just had a miss?  That was a rare one that I've never seen before and some awesome skill to find!