[mut]

This is asking about a 1975 CB750K

I just got my new electric ignition and dyna dual output 3 ohm coils.


As you can see in this first picture, there were no coils or spark plug wires when i bought the bike.

I am having trouble figuring out how to wire it. The dyna wire instructions and the Clymer manual assume you are replacing coils, not starting from scratch.

The second picture shows the wiring harness wires that need to be connected.

Do any of you know what each of the wires are? Can you tell me which wires to connect to the coils?

The wires in the second photo are, from left to right, Yellow, Blue, Black/White, Green, Black.

The Honda manual says to connect the yellow, blue, and Black White leads to the wiring harness. The dyna coils have 2 connection points on each coil.

Also, the second picture shows 5 wires and there are only 4 connection points??

Finally, someone told me not to forget to ground the coils. As you can see there is no mounting bracket with the bike. I will have something fabricated once I tear this bike down, but for now I need to temporarily mount them so I can make sure she runs. If I use hose clamps to mount the coils, do i just need to connect a wire from either side of the coil to the frame somewhere? Or do i need to ground both sides of the coil?

 

[mut]

Just after posting I went back to look at all the diagrams that I have.

I now think that the yellow goes to one coil, the blue to the other, and the white/black gets split with one lead going to each coil.

Is that right?

If so, how do I ground the coils?

What do the green and black wires go to?

Thanks,
Mut

 

[xander450]

Well, being that I'm lazy and don't feel like searching for a wiring diagram, why don't you find one for us and post it?

...but, generally speaking, the three wires you've got OUGHT to do it. In a stock setup, yellow and blue go to your points, black/white goes to your coils, and black and green are probably for a different system - most likely your horn, which would be mounted in the same place. Either way, black should be hot and green is ground, so if you need a hot wire or a ground, there they are.

Is the EE a Dyna as well? If so, it should be supplied with a harness of its own, in which case all you need is the black/white lead - you can ignore the others entirely. Otherwise, I suspect the yellow/blue wires resurface somewhere - in a std setup they run between the points and coils, so they don't have far to go.

Where are you at on this?

 

[mut]

Here is the diagram. I had to take a picture of it and zoomed in on the coils part.

As far as where I am: I changed the oil. I have a new battery, dyna electric ignition, rectifier, and am putting it together so I can start it and see how it runs. I am taking ( i think) your advise and getting it working 1st then tearing it down to do the cosmetics.

The electric ignition is supplied with its own harness. I think it is designed to plug into the original harness, which it does.

Do you have a take on how to ground the core? I am assuming that if you connect the coils to the bike with the stock mounting hardware you would also be grounding it. Since I plan to use hose clamps i will need to ground the core. I think I know what this means, we'll see.

We'll see if it runs.

 

[mikeo]

Black and white should go to ground. You should also mount the coils with the mounting bolts threading into a grounded frame bracket. The existing mounting bracket for the old coils should work.

Mike O.

 

[xander450]

MikeO,

At that stage in the system, black/white is hot - if it goes straight to ground, the coils never fire (not to mention that wire probably burns).

The black/white carries power to the coils, and the yellow and blue wires give the coils a return to ground which, when unavailable (i.e. points open), causes the coils to take the next available path to ground - across the plugs, exactly what you're after.

SO, b/w is hot and you still need a ground strap. I'd try mounting the way you were intending and see if the ground straps are conductive enough to give you a good ground to frame. If not, you could solder a good fat wire across the coil bodies and bolt it to the frame.

A

 

[mikeo]

Xander,

Good catch. You're right, my bad. It was late at night and I wasn't thinking too clearly. Last time I messed with a stock Honda ignition it was to strip it all off and put on a Nutronics electronic one. Sorry for any confusion.

Mike O.