Honda CB750 Sandcast

hooking the field coil back up

cb750k0 · 14 · 7208

cb750k0

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I posted this on the SOHC site, but didn't get any responses, so I thought I'd try you guys. I'm putting my bike back together (CB750K0) and can't remember how it came apart. There's 2 wires coming from the field coil, hooking up to green and white wires, but there's no coding on the coil. I'm assuming it doesn't matter which way these go, correct? Thanks, John.


markb

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I'm assuming you're talking about the 3 yellow wires.  Yes you're correct, it doesn't matter which goes where.
Mark B
1969 CB750 sandcast #97 restored - Sold Restoration thread link
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1969 CB750 sandcast #1990 - Sold
1969 CB750 sandcast #5383 restored - Sold Restoration thread link
1970 CB750 K0 restored - Sold
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cb750k0

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No, sorry Mark, that's the stator wires (yellow). The field coil has only 2 wires, and they go to Green and White. But there's no matching color on those wires, so I'm assuming, like the yellow wires, it doesn't matter. I'm just trying to make sure before I start it up. Thanks


kmb69

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I don't think the field coil wires matter either. Both of the field coil wires should be insulated from ground. It is just an electromagnet with voltage controlled by the regulator. I do not think the polarity would make any difference since the stator is producing AC.
« Last Edit: May 23, 2011, 01:20:26 pm by kmb69 »


markb

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Oops, didn't read carefully enough.  Someone may chime in before I get a chance, but I will look at a coil.  Seems like I remember colored bands on or near the connectors for the coil.
Mark B
1969 CB750 sandcast #97 restored - Sold Restoration thread link
1969 CB750 sandcaxt #576 - Sold
1969 CB750 sandcast #1553 - Sold
1969 CB750 sandcast #1990 - Sold
1969 CB750 sandcast #5383 restored - Sold Restoration thread link
1970 CB750 K0 restored - Sold
2010 H-D Tri Glide Ultra Classic (Huh?)


cb750k0

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Yeah, I couldn't find any on mine, or they were too discolored


markb

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I took a look at one of my coils.  At first I thought the wires were the same color but after looking closer and pulling back on the braided sheath covering the wires I could see that one of them was definately white.  Don't know if it matters which way it's hooked up but I would double check the wires and match them.
Mark
Mark B
1969 CB750 sandcast #97 restored - Sold Restoration thread link
1969 CB750 sandcaxt #576 - Sold
1969 CB750 sandcast #1553 - Sold
1969 CB750 sandcast #1990 - Sold
1969 CB750 sandcast #5383 restored - Sold Restoration thread link
1970 CB750 K0 restored - Sold
2010 H-D Tri Glide Ultra Classic (Huh?)


Wayne

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Unless these coils are different, in my experience hooking a coil up backwards will cause the spark to jump from the ground of the plug to the electrode. Not good for plugs or coil.
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cb750k0

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Ok, I better look again then. It sorta seems that if the wires that they plug into are green and white, they must need to match up. The 3 stator wires are all yellow on either side of the connections, so it makes sense they don't matter. I'll get out the microscope
Thanks guys


kmb69

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I would agree if we were talking about the ignition coils with primary and secondary windings but the question is regarding the field coil in the altenator.

The field coil is just an electromagnet. The 2 "wires" are actually each end of the same wire. It is simply an insulated winding around a steel core. The voltage regulator senses voltage at the battery and supplies variable power on one side and provides a ground on the other to create a variable strength magnetic field.

You will not damage any thing if they are connected backwards.

When polarity is critical, Honda uses a combination of male and female connectors to prevent getting them wrong. In this case, the field coil wires both have male connectors with the females on the wiring harness. I know it will make you feel better if you can identify the colors and connect accordingly. Maybe you could use some electrical contact cleaner to wash the oil and grunge off the wires to see some color.



Wayne

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Sorry for the confusion. Threw me off referring to a stator as a "coil". Should have read the posts better.
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cb750k0

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ok, thanks again guys. I'm feeling pretty good about leaving it alone. I looked pretty close before I put it back together and couldn't see any color. I'm not really wanting to hack into that insulation on the wires.


markb

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You shouldn't have to hack in to the insulation on the wires.  The braided sheath is flexible enough to pull back and expose enough of the two wires to identify the colors.  But it appears the consensus is it won't matter anyway.
Mark B
1969 CB750 sandcast #97 restored - Sold Restoration thread link
1969 CB750 sandcaxt #576 - Sold
1969 CB750 sandcast #1553 - Sold
1969 CB750 sandcast #1990 - Sold
1969 CB750 sandcast #5383 restored - Sold Restoration thread link
1970 CB750 K0 restored - Sold
2010 H-D Tri Glide Ultra Classic (Huh?)


cb750k0

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well, just to close out this thread, I took off the side cover today to re-inspect those field coil wires. They both looked black and are cloth covered, but when I cleaned them up with butane, they are indeed green and white, and I actually had them right anyway! So, it may not matter, but probably does matter since, they ARE colour coded.  Thanks guys. Fingers crossed, the K0 is almost done and I'll try and start it this week.