Found something… pics coming soon!

[made2care]

Aaaaahh… the old hammer tap on starter trick brought old starter back to life for a while. Still need to change the pg and hopefully I will have spark after that!!

 

[made2care]

If I put a test light on the wires ( not spark plug wires) going to coils and crank the bike, should that light up and then go off?

 

[DaveO430]

The yellow & blue wires should flash on & off, the black should remain on.

 

[made2care]

The yellow & blue wires should flash on & off, the black should remain on.

Alrighty then. Thanks for the info. Will check

 

[made2care]

Cranked bike and nothing from yellow/ blue wires. Black remains on.

 

[made2care]

Where are the wires going to the coils coming from?? Pulse generators or cdi box or both??

 

[DaveO430]

The black/white is from the kill switch, the blue & yellow are from the ignition control unit (it is NOT CDI). If there is power to the coils and nothing on the blue or yellow then power is not getting through the coils.

 

[made2care]

Installed new pulse generators and a new starter. Tried a different icu off of a running bike and still nothing in terms of no flashing on my test light on blue/ yellow wires going to coils when cranking bike.
Very perplexing!

 

[made2care]

There’s a short somewhere. Can’t even reconnect battery terminals as it’s popping pretty badly! Will keep checking!

 

[made2care]

Removed entire wiring harness. Have an extra … will install that one.

 

[kerryb]

The 78 might not need engine work yet. Do a compression and leakddown test before opening it up much. If you don't already know, the www.forums.sohc.net site is a wealth of info on that bike. Those engines can go to pretty high mileage if maintained well.

 

[DaveO430]

Installed new pulse generators and a new starter. Tried a different icu off of a running bike and still nothing in terms of no flashing on my test light on blue/ yellow wires going to coils when cranking bike.
Very perplexing!

Did you try new coils, that is what was indicated by the test.

 

[DaveO430]

There’s a short somewhere. Can’t even reconnect battery terminals as it’s popping pretty badly! Will keep checking!

Probably the starter solenoid stuck.

 

[made2care]

Probably the starter solenoid stuck.

Yup… gone through 2 solenoids now. I have not tried new coils yet. I’m placing my test light to the wires that connect to the coils but have them disconnected from the coils while testing. Still no light on and off while cranking…. I like a challenge but I’m about to move on to something else!

 

[julimike54]

The black/white is from the kill switch, the blue & yellow are from the ignition control unit (it is NOT CDI). If there is power to the coils and nothing on the blue or yellow then power is not getting through the coils.

Looking at the above underlined. My understanding is the Black/White is "hot" all the time, in normal operation. The Blue or Yellow is how ground is supplied to the coils, hence the hot now has a ground and the coil will fire. The grounding is controlled by the Ignition Control Unit (ICU). Without the signal wires connected to the coils you may not see a change to the Blue or Yellow wires. If you have an open coil winding the circuit would not complete either. I'd check your primary coil windings Ohm value to see that both are equal in value and that neither is 'open'. You need to have at least one of the wires off both coils the check this or you could get a false reading.

 

[made2care]

Hallelujah!! Got the bike running and I have no idea what I did!! Still have to check to see if I have spark to all 4 but hey… at least she’s up and running. Thank you to everyone for all your insight on this one. I was ready to throw in the towel!

 

[made2care]

Thank you julimike54 for clarifying. This is still a mystery as initially the bike had no spark and obviously fuel pump was not sucking fuel. I was hung up on a YouTube video showing the blue/ yellow coil wires unplugged and the guy had a test light on that wire that lit up upon cranking… mine didn’t so I assumed my icu or pg was bad.
Anyway…. Huge relief she running and now I can begin my build.
Thanks again to all who responded.

 

[julimike54]

You're welcome. Like I stated of presumption, I'm using my electronic function/design basis. Typically the design is that the computers or electronic circuit boards do not turn 'power on and off' they only turn a function on or off by 'grounding', this is done to help the longevity of these parts.

Best of luck!

 

[made2care]

Loud ticking from front. Here’s a video

 

[dan filipi]

Ive heard that before with one tooth off on the timing belts