70 up charging system upgrade question

Not sure what cranking voltage is at battery. Difficult to do as doing this by myself for most part.
Doesn't matter. Your other test showed no problems in the wiring, we know its around 11 Volts and you can hear the starter is turning fast enough that it should start, that's close enough.
Your hand drawn diagram is fine. I could copy it, turn it 90 degrees and read it.

Got a "good deal" on all new 70 up stuff.(alt & vr) and got new ecu, ballast resistor and coil.
Did the 70+ upgrades correctly I believe.
Now cant get it to start properly.
Hard to know if this relates or not. Always a possibility it could be ECU. Less likely coil because you heard it fire off once on release from start.
It could be timing, it could be in the start switch, it could be fuel, or compression.
Lets eliminate the possibilities one at a time. Start with spark because electric is the area where things were changed.

The best and safest way to check for spark is one of these testers.
31GcuD3PIqL._SL500_AC_SS350_.jpg
Less than 10 USD and I'm sure you can find one at any autpo parts or small engine store.

Put it on a spark plug where you can see it while turning the start switch.

A slightly different test will be to put the key in run position. This one is only needed if the first test shows no spark.
Then take a jumper, or a screw driver with an insulated handle, and provide power from the battery to the start relay. In other words jump the main power from the stud to the terminal with the yellow wire. The solenoid will energize on and the starter will crank. The difference is the ignition will be getting power through the blue RUN wire instead of the brown START wire.