'77 CB750 point probs

[jamman18]

Just to clarify....run wires from positive battery terminal to bothblack inputs for the primary saides of the coils?

[TOOLS1]

Thats it.
TOOLS

[jamman18]

Sorry, just to be specific....once these are attached, then power on the bike and run the starter to see what happens?

[TOOLS1]

Yep that's it. What you will be doing is hot wiring it. If you get spark, and it runs like this; then you will know it is a wiring problem. If you do not care weather or not it is stock perfect, I can hook you up with a simplified wiring diagram. You should be able to rewire it yourself.
TOOLS

[jamman18]

Ok, I did the bypass and I did get spark!  So instead of actually finding the short, you are saying that you can help me fix this in another way by rewiring?  BTW, I do have the stock wiring diagram that came with the manual.  What should I do next?  Feel like we're gettin' close!

[TOOLS1]

Now you could do two different things. If your wiring is in bad shape then I would just rewire it. If the wiring is still pretty good it might be worth while to find the short. The first 2 places I would check would be. The ing switch, and the kill switch on the right handlebar controls. You cab do this by dis connecting them and using a jumper wire to bypass them (just like you did with your hot wire). If you get spark when jumping them one at a time you will know where the short is. My guess is the ing switch.
TOOLS

[TOOLS1]

Try jumping the Blk, and Blk Wht wires on the kill switch first. I will bet that is the problem. If not try jumping the Red, and black wires on the ing switch.
TOOLS

[jamman18]

Don't know if this means anything or not, but as in my previous post, the ignition switch connector has been disconnected and the red and black wires (I believe) have been bypassed into a toggle switch that runs main power to the bike. Not sure if this would eliminate any issues with the ignition and kill switches or not.....just wanted to throw that out there....

[TOOLS1]

I must have missed that post. I would certainly suspect the toggle switch, or the connectors. Try by passing it, and use new connectors.
TOOLS

[jamman18]

Yeah, here's the original post.....just FYI....

"Well, I tested the coils as you said by checking ohms with 1 probe on black primary and the other to the yellow and blue
wires respectively. Then tested the 1-4 and 2-3 coil plug wires with the caps off.  I got readings of zeros on all these so
from what I understand about continuity, these are the readings I should get for good coils.  That being said, here is what I
do know at this point: the plugs are good, points and condensers new and adjusted right. I have 12v through to the points.
The bike HAS started and run 3 times since this problem began. I have continuity through both sides of both coils. When I try
to get a spark on the plugs by holding the plug against th eengine block I get no spark, although I have before the bike
started the 3 other times.

(The ignition switch has been bypassed by a main toggle switch which renders the ignition switch
and kill switch inactive. I just toggle the power on to start the bike and toggle off to kill the motor.)

The starter runs
fine. By everything I know, the bike SHOULD work but it doesn't.

Let me ask this: can the timing be so far off that it won't let a charge go through to the plugs to get a spark?  Seems to me
if it was running before (very well too!) that this would not be an issue but I'm grasping for straws at this point.  Seems
that there is more likely an intermittent short that occurs somewhere in the wiring that is keeping the bike from
starting....but WHERE I don't know since the only thing downline from the points where I AM getting power are the coils which
seem to be working fine. Did I test these correctly?  Any other suggestions? "

[TOOLS1]

I guess that did not sink in
I would suspect the toggle switch for sure. It might be bad, or not able to handle the amps required for the bike to run. I would definitely try bypassing it.
If the wiring has been cobbled by some previous 12 volt electrician I would definitely rewire it. Here is a simple wiring diagram that cuts out all the bull crap.

  

TOOLS

[jamman18]

I guess what I'm wondering about the possibility of the toggle switch or connectors being bad, is that if they were then I shouldn't be able to get lights on and run starter as this switch controls both. But they run fine.  Just not sure what and where to bypass.  I guess I could try bypassing the kill switch although it doesn't operate now so I'm wondering what difference this could make.  The wiring is in pretty good shape aside from this one problem so I would really like to either find the short or just bypass if I can figure out where to bypass.  You mentioned bypassing or doing something different with the toggle switch.  Where exactly am I hooking up from and to?

[TOOLS1]

Just disconnect the wires from each side of the switch, and connect them together. From what you are saying about everything else working I would bet that the connector on the black wire is bad.
TOOLS

[jamman18]

I see.....I will check that......just still am trying to understand electrically, how the switch could run lights and starter but not the coils?  

[jamman18]

I took the toggle switch off and tested for continuity, which it had.  Then I connected the 2 leads together and still no spark.   Since I do get spark when connecting directly from the battery to the coils, I think what I am going to do is run a new connection from the battery to the coils with another switch in between. I'll just have 2 separate switches to turn on; one for the coils and 1 for the starter and lights.

[jamman18]

I got the new wiring and switch on to power on and off the coils seperately and the bike fired right up 5 times throughout yesterday!  This should do the trick! Thank you all for all your help!!!

[LukeM]

That is excellent news! Perseverance pays off.  Now get out there and RIDE THAT THANG!

Luke M

[jamman18]

Yeah, it's been almost 3 mths to the day, but of course now I have to deal with the snow and freezing temps.  There are some good days though!