Topic: Cb750k2 electrical problem?

[Odin]

Hi

Trying to wire up my bike with a completely new loom,and pretty much nothing is working, lighting up or anything.
Used a multimeter and went probing for power, and nothing has power execpt the black wires.

I never really thought about this before, but i assumed that black is supposed to be ground?

if it is correct that black is ground, what in the world is wrong? are these bikes suppers to have positive ground on the battery, or have i somehow switched around some wires elsewhere?

Since its a new loom, other than the big connectors that doesnt fit anywhere else, i hooked up the starter solenoid, rectifier, the fusebox, coils. Nothing is connected at the taillight, or any switches are connected either, cept for the ignition key.

Thanks in advance for any help

[greenjeans]

Is the frame grounded?   I'd check that first.   Also, the main fuse.  Negative from the battery will go directly to the frame.   Check the connection - make sure it's a good bare metal to bare metal connection.  Black is 12V switched (ignition)

[Bodi]

Black is switched battery power (+12V). Should measure 12V or so to frame/ground only when the key is ON.
There are some green ground wires in various places, the harness usually grounds via a wire to the frame - I think it is near the coils, maybe on one of the coil mounting bolts.
After that it depends on the model year, and I'm not sure about a K2. I believe early ones had only one fuse. Later models have 3 fuses and more complicated wiring. Regardless: a red wire with a sleeve (extra protection, shorting that one to ground - with no fuse- will get exciting in a bad way) goes from battery "+" or the starter solenoid (connecting where the fat positive battery cable goes) to the fuse or fusebox MAIN fuse, then to the keyswitch. From there, power goes either to all powered things (one fuse) or on to some powered things plus back to the fusebox where there are HEAD (headlight and some other stuff) and TAIL (tail light) fuses (three fuses).
The ignition coils power through the kill switch.
Neutral and oil lights are always powered, the ground is switched.
You nedd a high current ground connection between battery "-" and the frame and engine cases, normally to a ring terminal on one of the engine hanger bolts.

[Bankerdanny]

The black = power confused me too when I got my first old Honda.

Download and print out a wiring diagram, color if you can. If you have a color printer at work that can print to 11x17 paper even better.

[Odin]

Thanks for your answers.

Oki, then it must be the black switched power i probed, so one step further on that.
My bike has only 1 fuse, on the red smaller wire, that comes from the big red wire from the starter solenoid. I probed after the fuse and that one has power.

battery negative is hooked to frame engine mount bolt, another green smaller groundwire is grounded in the seat lock area. i didnt notice any ground in the coil area but will double check

Is it normal that the dark green wires inside my headlightbuckett doesnt have power when i havent hooked the  handlebar switches up? from what i could tell looking at the electric diagram, they go to the headlights amongst other things.
for some reason i also thought they would be switched 12v, but actually its the black they get power from?

Is there any other wires cept black that should have power when key is switched on in the headlight buckett? just from memory from earlier today, it seemed to me many of the control switches, instrument lights, etc, has one black wire as well, i guess all these blacks will get power from the black switched in headlight then?

Thanks again for your help!

[TwoTired]

The FAQ has a list of standard Honda color code assignments.  Green is normal for inside the headlight bucket.  All devices must get both a POS and NEG connection to the battery for them to work.  Device NEG is normally a constant connection via the Green wires.  The device POS connections are switch controlled, branching off the black wire if a control is required.  Most switches will have a black wire connection.

The wire loom should only have on connection to frame ground.  This is so Honda could control the electrical current going through frame joints where water can get to.  This can lead to electrolysis corrosion, eat your frame from the inside out.

Is it normal that the dark green wires inside my headlightbuckett doesnt have power when i havent hooked the  handlebar switches up? from what i could tell looking at the electric diagram, they go to the headlights amongst other things.
for some reason i also thought they would be switched 12v, but actually its the black they get power from?

Unconnected green wires will have voltage on them if they don't have a solid connection to battery NEG.  Headlight filaments will directly bridge voltage to green wires if they don't have that NEG battery reference connected.  Worse, if some lights do have the proper reference, they will light if other lights don't have proper connections.  This is called ground/return issues.
The forks are the usual connection issue.  The harness must provide the green connection to the bucket.  The fork ears are rubber isolated.  So, there is a headlight mounting nut with a connection to harness ground (Green). This is the way turn sigs get their ground reference.  And you DON'T want the sigs to find ground through greasy fork bearings.

Cheers,

[Odin]

Thanks again for your answers.

Now i think i got the workings on the wires straight, So  tomorrow i will do some more probing and hook everything up and hopefully i get them working like they are supposed to.

Thanks again for your help 

[PeWe]

I have recently built a K2 with new aftermarket main harness, cheap aftermarket handle bar k2 switches, NOS k2 ign switch + the rear wires from Yamiya. Connected everything and correct direct!
I had verified all wires from both switches with buzzer, marked all wires with tape and pen. I even added the winker buzzer.

Stock pilot lamps and gauges with ilumination + parking light front where the additional single brown wire is used.

One thing I have noticed with the cheaper Aftermarket harness is the weak connectors. Stock has thicker mtrl which is seen on sockets that can become too stretched out too easy. Needed to squeeze them tighter.
Lets see if I need to replace all sockets after a few years with better.

[HondaMan]

One thing I have noticed with the cheaper Aftermarket harness is the weak connectors. Stock has thicker mtrl which is seen on sockets that can become too stretched out too easy. Needed to squeeze them tighter.
Lets see if I need to replace all sockets after a few years with better.

Thanks for the tip, PeWe! I just got in my new K2 harness, haven't even unpacked it yet. I'll look those over, for sure. I have LOTS of the little connectors, used in my Ignitions...and the ones from Vintageconnections are superior. BTW: vintageconnections.com belongs to a new owner, now... so far, I've been getting the same good parts from him/them, though.

[PeWe]

One thing I have noticed with the cheaper Aftermarket harness is the weak connectors. Stock has thicker mtrl which is seen on sockets that can become too stretched out too easy. Needed to squeeze them tighter.
Lets see if I need to replace all sockets after a few years with better.

Thanks for the tip, PeWe! I just got in my new K2 harness, haven't even unpacked it yet. I'll look those over, for sure. I have LOTS of the little connectors, used in my Ignitions...and the ones from Vintageconnections are superior. BTW: vintageconnections.com belongs to a new owner, now... so far, I've been getting the same good parts from him/them, though.

Yes Mark, the connectors you use on your ignition are really good. I had thoughts to ask you where you buy them.  Now I know
I have bought some cheap sockets and pins kits from China for very few $, they are thinner.