yeah dead battery. Needs to be above 13v and above 11v when cranking so ECU works. To force in 9v, just use little test-leads with alligator clips and clamp onto solder-lump underneath ignition switch. Or trace to harness connector and back-probe connector with nail in pink position. Then clamp alligator clip onto nail. Measure pink wire at ECU connector to verify 9v is actually arriving.

But, main problem right now is dead battery.

 

Today's test results:
My battery is getting a workout and it cranks the engine fine for many, many start attempts.
Battery at rest = 13.50 volts.
Ignition switch 4 points - 1) At red/black wire solder point = 11.52 volts 2) At Zener Diode anode = 11.48 volts 3) At Zener Diode cathode = 11.48 volts 4) At solder of pink wire = 11.47 volts
Action - Took the 3.9 volt 1W Zener diode out as my readings at the ignition base are not correct. Soldered in a 3 volt 1W (IN4727A) Zener diode as that is the smallest value I have available at this time until a new diode kit is delivered that has 2 volt and up.
Updated measurements for ignition switch 4 points (with 3V diode installed) - 1) At red/black wire solder point = 11.53 volts 2) At Zener Diode anode = 8.36 volts 3) At Zener Diode cathode = 11.53 volts 4) At solder of pink wire = 8.38 volts. Battery voltage at rest during this test = 12.60 volts.
Attempted to start engine with pink wire at 8.38 volts and no luck.
Forced / bumped up pink wire voltage to ECU by connecting external 9 volt DC power supply to solder point of pink wire at base of ignition switch. Confirmed I was getting 9 volts at ECU connector by back-probing.
Choke on, engine stop switch in ON, tried to start and still nothing, no combustion. Hooked up battery start-boost and continued start attempts without success. Not even a chug.
Should I purchase a new battery? Current battery is a Yuasa YTX9-BS. My previous Yuasa battery lasted ten years in this motorcycle.
Plan to install a lower value Zener diode to get my pink wire voltage to 9V.
I am installing the black stripe of the diode closer to the pink wire solder connection of the ignition switch base. I am copying what Honda factory had with their diode installation. The factory diode stripe was positioned close to the "notch" of the top rim of the plastic diode cradle support. Is this correct?
I am not making much progress and the frustration builds.

 

I dont believe replacing your battery at this time will result in a different outcome. At good battery at rest should stand at 12.8v. I think that forcing 9v to the pink wire at the ecu and still experiencing a no start symptom, means we need to start looking at other possibilities of faulty components.

 

Does Honda certified service have the ability to plug-in and read codes like OBD for this issue? They may be able to quickly find the root cause of the no start and drain my wallet.

 

I dont believe there is a diagnostic port to plug into.

Digging through the service manual, here is what I found on battery specs.
Fully charged 13.0v - 13.2v
Needs charging below 12.3v

 

So here are some things I think you should check at the ICM connector.
G to ground should be low ohms
LG to ground should be low ohms only when in neutral
GR/W should be low ohms only when side stand is up. Should be O/L when down.
Y to Y/W should be the same reading as your pickup coil ohms (measure ohms at pickup coil connector then compare to ICM connector. Should read the same value)

These next reading should be taken with ignition on and engine stop switch in the "Run" position.

At the ICM connector
Bl to ground should equal battery voltage

At any ignition coil connector
BL/W to ground should equal battery voltage.

 

Shouldn't be spending money on anything yet. Let's do some more testing. Sorry I skipped ahead because it seemed simple. But we need to start from very beginning to prevent wasting time randomly jumping around.
Let's do this first test to verify battery condition:

1. measure battery voltage with everything OFF

2. measure battery voltage with key ON, kill=RUN

3. measure battery voltage when pushing start-button

4. measure voltage on blk/wht wire ECU connector when pushing start-button

5. measure voltage on blk/wht wire at ignition-coils when pushing start-button


Also post photo of diode and how you have it installed. So far, I have yet to find single photo on entire internet with it installed properly.

And post photo of rear section of ignition-switch. The section that faces frame with locking pin.

 

Photo of my ignition switch base with new 3V 1W (1N4727A) diode installed. Solder would have been done better but I intend to remove this and install a lower voltage diode soon.
This diode did result in better output to the pink wire at 8.38 volts. Previously the 3.9V 1W diode that was taken out likely was failed as the pink wire voltage was 11.47 volts.

Zener diode of ignition switch base.
My other testing completed today did not save and send so will perform the tests again later and provide results.

 

Battery Testing Sept. 16/23

1. measure battery voltage with everything OFF = 13.16 volts

2. measure battery voltage with key ON, kill=RUN = 12.06 volts

3. measure battery voltage when pushing start-button = 11.14 volts

4. measure voltage on blk/wht wire ECU connector when pushing start-button = 10.67 volts (Wire at ECU is all black and located 2nd from the bottom on the outside row of terminals.)

5. measure voltage on blk/wht wire at ignition-coils when pushing start-button = 10.35 volts (Measurement taken from the spark plug coil connector of the far-right side cylinder.)



Checks at the ICM connector.

G to ground should be low ohms = 0.3 ohms (Measurement taken from the open disconnected ICM connector of the dark green wire.)

LG to ground should be low ohms only when in neutral = 18.5 ohms with bike in neutral. With bike in 1st gear measurement from LG wire = reading OL or open. Readings from LG wire jumping around with bike in neutral.

GR/W should be low ohms only when side stand is up. Should be O/L when down. = reading OL (open) with side stand down. Reading 1.9 ohms with side stand up.

Y to Y/W should be the same reading as your pickup coil ohms (measure ohms at pickup coil connector then compare to ICM connector. Should read the same value). Y to Y/W wire of pickup coil = 15.18 M ohms (with black probe to white wire of red pickup coil plug). Did the same test using red probe tip to white wire of red plastic pickup coil connector = result 44.72 M ohms. Reading bouncing around quite a bit.

Note – The red connection plug for the pickup coil is in a terrible location and hard to get at. I used two Crescent brand X2 long nose pliers and was able to get the plug by reaching in above where the clutch cable connects to the lever at the right-side engine cover. These pliers are a must have, in any mechanic’s toolbox.

Reading of ICM terminal for pick up coil = 23.25 M ohms (yellow wire to wide white stripe yellow wire at ICM connector terminals).

Next reading taken with ignition on, and engine stop switch in the "Run" position.

Battery voltage at rest = 12.60 volts

At the ICM connector

Bl to ground should equal battery voltage = 11.47 volts

At any ignition coil connector

BL/W to ground should equal battery voltage = 11.37 volts

 

So based on that diagnosis, I would suspect your pickup coil. The reading at Y and Y/W at the ICM should read the same as measuring the pickup coil at its connector down by the clutch cable. That ohm reading sounds awfully high too. I think its supposed to be around 400-600 ohms but I'm having a hard time confirming that in the manual.