Topic: Why might the front L/R running lights not be working?

[drumstyx]

'78 750K -- Just switched to LEDs and I've been testing everything out with rough wiring (my headlight bucket is off getting painted). Is there anything more than ground and Orange/white (or blue/white) that needs to be connected for the 'low beams' of the front signals to work? The headlight works, the high beam works, flashers work (L/R 'high' beam), and I can even get it to light when I apply 12V directly to the orange/white (blue/white) wires.

What am I missing? It worked fine before (though now it doesn't work even with the old bulbs)

Diagram for reference: http://www.oregonmotorcycleparts.com/Diagrams/CB750k8.jpg

Only thing I can think of is something wrong with the switch, but it's just so odd that it'd show up now. It's quite a complicated switch too...

[mrbreeze]

Try running a jumper from the bulb housing to a good ground. If the positive wire has 12v it should work. If you have the headlight bucket off you have taken away the ground. Also make sure the headlight switch is turned on to supply the power to those filaments.

[drumstyx]

Looks like I might have mismatched left hand controls. Brown/white from the left hand controls needs 12v, as opposed to HL2 providing it as per the K8 diagram. To add to the problem, the brown/white block from the harness doesn't have 12v until a weird little jumper wire (brown/blue, I think?) is connected to black...so when I had everything hooked up, it didn't work because I was missing the jumper.

And to think, I actually took apart the whole darn thing because I couldn't find continuity between HL2 and the applicable wires...

EDIT: but who knows...here's another '78 LH control with the same brown/white wire that doesn't appear on the diagram: http://www.ebay.com/itm/1978-Honda-CB750K-CB750-750K-left-hand-controls-switches-horn-signal-/142139895825?hash=item211832b011

[TwoTired]

The front forks are not a reliable ground (head bearing grease).

Honda ran the green frame ground into the headlight bucket for ground return of the lamps.  Is it disconnected there?

[drumstyx]

I figured it out, but for a ground I had the ears connected directly to the main frame ground with alligator clips. I've got those grounding nuts for inside the bucket when I put it back on.

[jonda500]

The front forks are not a reliable ground (head bearing grease).

Honda ran the green frame ground into the headlight bucket for ground return of the lamps.  Is it disconnected there?

When sounding the stock honda horn, doesn't it ground through the steering head bearings?
John

[kerryb]

On the 550, the horn is grounded through the horn switch.  On my k8 750 there are two wires from the harness to the horn, black  (hot) and white which must lead back through the switch and then to ground.  Thus bypassing the iffy ground path through the head bearings.

[drumstyx]

The horn is 100% grounded through the bars, which in turn grounds through the bearings. That's a pretty minor and intermittent load though. That said, properly preloaded bearings should have no issue carrying current.

[TwoTired]

That said, properly preloaded bearings should have no issue carrying current.

I suppose that is true enough.   I will point out that passing current through them will hasten corrosion when there is any moisture contamination.  Two metals with electrolyte between them and a current passing though.   Not exactly a good idea.   But, as you say it ought to be a rare occasion thing.