Author Topic: CB550K1 - electrical issue - locations of junction in cabling  (Read 283 times)

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Offline Erny

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CB550K1 - electrical issue - locations of junction in cabling
« on: February 07, 2019, 09:11:38 am »
Can someone navigate me where exactly to find 3 junctions on "Bk line" as per attached diagram that are between IGN switch and headlight?
I do not have +12V on one of them in the headlight But as both are black I actually do not know which one it is. Before cutting/destroyoing sleeve and tape, I'd like to minimize damages...

Attached also pic of my bike, maybe for better clarity somebody can draw it here, where exactly I should cut


CB750K K7 USA model (1977)
CB550K1 USA model (1975)

Offline Erny

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Re: CB550K1 - electrical issue - locations of junction in cabling
« Reply #1 on: February 07, 2019, 03:16:12 pm »
no ideas?
CB750K K7 USA model (1977)
CB550K1 USA model (1975)

Offline my name is nobody

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Re: CB550K1 - electrical issue - locations of junction in cabling
« Reply #2 on: February 07, 2019, 03:41:38 pm »
Find which black is the shortest (From ign switch maybe?) and trace it. Make small slits
along the way to keep track of things. Re tape over slits when you find what you're looking for.
Use razor blade carefully.     Any solid black should be 12v when key is turned on. Any chance
a previous owner has done some "repairs"? Not quite clear on what your trying to find by locating those junctions. just curious..
« Last Edit: February 07, 2019, 04:06:23 pm by my name is nobody »

Offline calj737

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Re: CB550K1 - electrical issue - locations of junction in cabling
« Reply #3 on: February 07, 2019, 04:33:23 pm »
The junctions are either in the headlight, or beneath the gauge cluster.
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Offline bryanj

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Re: CB550K1 - electrical issue - locations of junction in cabling
« Reply #4 on: February 07, 2019, 11:49:32 pm »
Cal there are some crimped and/or soldered joints in the body of the loom which can sometimes, but rarely, come apart-----usualy by mechanical damage.
Semi Geriatric ex-Honda mechanic and MOT tester (UK version of annual inspection). Garage full of "projects" mostly 500/4 from pre 73 (no road tax in UK).

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Offline Erny

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Re: CB550K1 - electrical issue - locations of junction in cabling
« Reply #5 on: February 08, 2019, 01:17:43 am »
Cal there are some crimped and/or soldered joints in the body of the loom which can sometimes, but rarely, come apart-----usualy by mechanical damage.
Bryan, can you be more precise where they are to avoid cutting whole loom sleeve?

The issue I have is that 1 of 2 terminals (Black wire) that are coming from main loom into headlight does not have +12V (IGN ON). Issue is obviously between terminal and junction point. That's why I'm looking for it - I do not want to strip whole loom, just part that is absolutely necessary...
« Last Edit: February 08, 2019, 02:27:49 am by Erny »
CB750K K7 USA model (1977)
CB550K1 USA model (1975)

Offline bryanj

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Re: CB550K1 - electrical issue - locations of junction in cabling
« Reply #6 on: February 08, 2019, 03:13:29 am »
No idea exactly where the junctions are as i have never stripped a 500 loom, but having done others i would guess that they are somewhere between where the ignition switch spur is and the plastic piece round the headstock BUT I EMPHASIE that that is a pure guess.
Semi Geriatric ex-Honda mechanic and MOT tester (UK version of annual inspection). Garage full of "projects" mostly 500/4 from pre 73 (no road tax in UK).

Remember "Its always in the last place you look" COURSE IT IS YOU STOP LOOKIN THEN!

Offline Erny

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Re: CB550K1 - electrical issue - locations of junction in cabling
« Reply #7 on: February 08, 2019, 03:21:43 am »
Ok. So maybe somebody else who stripped it already will comment
CB750K K7 USA model (1977)
CB550K1 USA model (1975)

Offline my name is nobody

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Re: CB550K1 - electrical issue - locations of junction in cabling
« Reply #8 on: February 08, 2019, 04:01:44 am »
No idea exactly where the junctions are as i have never stripped a 500 loom, but having done others i would guess that they are somewhere between where the ignition switch spur is and the plastic piece round the headstock BUT I EMPHASIE that that is a pure guess.




I just checked a 750 harness of the same year as your 550, (very similar) and that is spot on.
in the harness where the keyswitch wires branch off the main harness, from what I saw.

FWIW
« Last Edit: February 08, 2019, 04:17:53 am by my name is nobody »

Offline Bodi

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Re: CB550K1 - electrical issue - locations of junction in cabling
« Reply #9 on: February 08, 2019, 04:13:13 am »
Try a wire tracer. This has a transmitter sending some signal onto a wire, and a receiver probe that senses it and beeps when the tip is close to the connected wire. You should be able to follow the harness until the beep stops: that locates the break.
I use one often when doing multiple speaker wire runs in cinema installations. Having the electricians who pull the wires hrough conduits label the wires is usually a waste of their time and mine as labels tear off in the pulling and mistakes are common, so we have to confirm the labelling anyway with the tracer or otherwise.

Offline Erny

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Re: CB550K1 - electrical issue - locations of junction in cabling
« Reply #10 on: February 08, 2019, 03:43:31 pm »
I think it should be here.
As I said one of 2 black lines in headlight is dead or had 1.5V less voltage that is unable to power needed equipment amd additionally the same issue for horn.. So I suspect there is one or 2 close joints...

Will report once I'll find what is root cause
« Last Edit: February 09, 2019, 12:32:32 am by Erny »
CB750K K7 USA model (1977)
CB550K1 USA model (1975)

Offline Deltarider

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Re: CB550K1 - electrical issue - locations of junction in cabling
« Reply #11 on: February 09, 2019, 06:37:52 am »
As I said one of 2 black lines in headlight is dead or had 1.5V less voltage...
Less voltage compared to what? Without the engine running it is not unusual to see a lower voltage. Is there a loss (= resistance) at the fuse box? At the IGN key switch? Erny, I see your location is in Slovakia. I have no knowledge of CB550Ks exported to Europe other than the CB550K3. I see that you use the CB550K1 wiring diagram. May I ask what the origin of your bike is and is it still in its original state? Or is it a CB500 that has got a CB550 engine? I ask you this because the wiring in Europe differs from the wiring in US models and not only for the horn...
« Last Edit: February 09, 2019, 09:47:14 am by Deltarider »
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Offline Erny

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Re: CB550K1 - electrical issue - locations of junction in cabling
« Reply #12 on: February 09, 2019, 11:05:44 am »
let's clarify.

Bike is CB550K1 original US model, imported from USA.
Diagram I posted is from this model and is correct (I'm 100% sure)

Issue was that there was no spark (no power on Bk/W wire on coils) and horn did not work too.
Everthing else looked to be working properly, incl idiot lights, flashers, starter was turnong full speed, rear brake light worked... (headlight was not tested however)

After tracing issue down from coils through kill switch (no power coming from headlight) into headlight case termination points, I found out that only one of 2 Bk terminals have full power (12V). Other one has less voltage by approx 1.5V or 0V (was unstable). So, I connected all Bk wires to working terminal and all except horn works, engine runs w/o any issue.

Horn has similar problem, Bk wire that goes from junction point from main loom shows the same behavior and Horn does not work. When I connected +12V directly from the battery horn works. It confirms issue in Bk line going from loom to Horn.

So my conclusion, 2 Bk wires that are coming from junctions I mentioned (1 in headlight case, 1 to horn) has some connectivity issue most likely around these junctions. Looks like semi-cut wire, bad soldering...

As all Bk wires are powered by same lead from IGN switch and fuse (red wire), there is no issue in fuse box or IGN switch...

I apologize if I'm not very clear, I'm not English native speaker
CB750K K7 USA model (1977)
CB550K1 USA model (1975)

Offline TwoTired

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Re: CB550K1 - electrical issue - locations of junction in cabling
« Reply #13 on: February 09, 2019, 06:53:16 pm »
You might verify your conclusion, by adding a jumper wire from a powered black wire to the devices you believe are starving for power.  If they work with the jumper wire, then you will need to break into the harness to find the break or corroded junction.  If they still don't work, then maybe the harness isn't the problem?

Cheers,
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Offline Erny

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Re: CB550K1 - electrical issue - locations of junction in cabling
« Reply #14 on: February 10, 2019, 12:54:30 am »
You might verify your conclusion, by adding a jumper wire from a powered black wire to the devices you believe are starving for power.  If they work with the jumper wire, then you will need to break into the harness to find the break or corroded junction.  If they still don't work, then maybe the harness isn't the problem?

Cheers,
This is exaxtly what I did (maybe not clear from my previous posts). All works with jumper wire... So, issue suspected in the loom
CB750K K7 USA model (1977)
CB550K1 USA model (1975)

Offline Erny

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Re: CB550K1 - electrical issue - locations of junction in cabling
« Reply #15 on: February 10, 2019, 03:41:14 pm »
So, issue found now.
As suspected, it was problem at junction.

For others that Bk wire junction is located in the middle of hard big sleeve that passes from coils around frame neck into headlight case.
I found that junction badly corroded, thus no conductivity.

Will need to fix by cutting wires and inserting piece of new wire in the middle & create new junction. Current wires are so corroded that they are impossible to solder.

I suppose there was water ingress from headlight side in the past.. (as other side of the sleeve is under the tank and was perfectly sealed)
CB750K K7 USA model (1977)
CB550K1 USA model (1975)

Offline Deltarider

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Re: CB550K1 - electrical issue - locations of junction in cabling
« Reply #16 on: February 11, 2019, 01:09:24 am »
Good you found it.
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Offline Erny

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Re: CB550K1 - electrical issue - locations of junction in cabling
« Reply #17 on: February 11, 2019, 03:02:47 am »
It's pity that junction is not located more close to coils (upper in the loom) , being right in the lowest part of the sleeve arc is the worst...
CB750K K7 USA model (1977)
CB550K1 USA model (1975)

Offline BRG-BIRD

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Re: CB550K1 - electrical issue - locations of junction in cabling
« Reply #18 on: February 11, 2019, 05:40:51 am »
Wow, glad you found the issue!
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