Author Topic: CB750 EMGO Wiring Harness solution! (PartsNmore, et al...) (Read 17827 times)

HondaMan · « **on:** July 21, 2012, 10:37:42 PM »

I've had 3 of the PartsNmore EMGO wiring harnesses show up here this summer, all with the same issue: no taillight/instrument light power, and/or blown taillight fuse. Here's the skinny:

It appears the EMGO wiring harness is a combination of the Euro and US market harnesses. So, the BROWN wire in the headlight (for those in the US) now IS IMPORTANT. It now feeds the fuse for the taillight and instruments lights. Trouble is, at least in US bikes, there is no feeder from the START button for this wire. So, to fix it, make up a male-to-male 3.0mm bullet connector jumper to join the extra BLACK single female (which you will now also find in the harness inside the headlight) to the BROWN wire. This will now feed the center fuse on the fuseblock. I can make a jumper like this for you, but it might not be worth the postage: you can also use a RED 3M wire clip-on splicer.

Trouble is: now the center fuse is too big, as it was the 7 amp headlight fuse, and should be the 5 amp taillight fuse. And, vice-versa, because this is how the harness was adapted to the plug. So, swap the headlight (7 amp) and taillight (2.5 or 5 amp, depending on year) fuses to fix this up. Now all will work again.

If you have one of my blade-style fuseholders, same rules: swap the 5 amp top taillight fuse to the 2nd-from-bottom position and vice-versa. You might wish to remove the HDLT and TAIL labels on the Brn and Blk wires when you do, as they will be lying to you now... $:-\$

Don R · « **Reply #1 on:** July 23, 2012, 09:10:50 AM »

Thanks for the heads up, I haven't finished my K0 installation yet but I know what to watch for if it too has this issue. I'll post what I find here.

DaveI · « **Reply #2 on:** July 23, 2012, 08:19:03 PM »

I have been struggling with this battle as well... except I tried a different attempt and may or may not have had good results?

I tapped the extra female brown/white switch control adapter to the spare brown/red through a small jumper.
I also wired up an additional plug on the red and brown wire coming from the headlight control and have one going to the brown and red female (check for the right continuity first) and the other male plug going to the brown female plug in the headlight bucket.

It seems to work except for blowing a bunch of 5amp tail light fuses. Couldn't seem to wrap my head around this one.

Nonetheless, I still think you need to jump the female brown/red and brown/white spare plugs for the headlight to work as they are not tied in together like they should be. This was for my 1974cb750K what year did you use?

Also, do you get continuity running from the brown/red to fuse block via the brown tail light cables, red power cables and anything else? I am but am still unsure of whether this is normal or not. I didn't on the old harness

HondaMan · « **Reply #3 on:** July 23, 2012, 11:17:36 PM »

Quote from: DaveI on July 23, 2012, 08:19:03 PM

I have been struggling with this battle as well... except I tried a different attempt and may or may not have had good results?

I tapped the extra female brown/white switch control adapter to the spare brown/red through a small jumper.
I also wired up an additional plug on the red and brown wire coming from the headlight control and have one going to the brown and red female (check for the right continuity first) and the other male plug going to the brown female plug in the headlight bucket.

It seems to work except for blowing a bunch of 5amp tail light fuses. Couldn't seem to wrap my head around this one.

Nonetheless, I still think you need to jump the female brown/red and brown/white spare plugs for the headlight to work as they are not tied in together like they should be. This was for my 1974cb750K what year did you use?

Also, do you get continuity running from the brown/red to fuse block via the brown tail light cables, red power cables and anything else? I am but am still unsure of whether this is normal or not. I didn't on the old harness

It sounds like you have tied the (instrument and tail) lights and headlight together. Try changing the fuse to 7.5 amps to see if it lasts longer, as the load is higher that way. If you have a halogen headlight as well, try a 10 amp fuse, but watch for heating fuse contacts. These will show up right away, and can melt the Honda plastic holder.

DaveI · « **Reply #4 on:** July 24, 2012, 11:55:42 AM »

I suppose I did. I'm going to re route it the way you have it and see how that helps.
My goal was just to have the headlight work. It took a while to realize but the headlight power (brown/red) isn't tied into the headlight switch control (brown/white) on these harnesses as it should be. You manually have to do that yourself

BrettPPR · « **Reply #5 on:** August 22, 2012, 03:53:31 PM »

I have also just come across this issue on my US K3.
In comparison to the original harness, I find when connecting all EMGO harness headlight connectors, the following 4 wires are "left over".
- brown/white, brown/red, brown, black.
To further confuse issues, the Emgo main harness has two brown/red wires in the headlight, and these have white shrink collars on them?
Are these white collars supposed to mean anything? Are they interchangeable as brown/white?
As there is only one brown/red wire from the left hand switch block, you have to choose which of the two brown/red harness wires to connect to - leaving the other one "left over"? Does it matter which one you choose?
From the above comments in this thread, are the following conclusions correct:
1) I do Hondaman's "fix" and make a jumper to connect the "left over" black and brown wires, and then fix the fuses as recommended.
2) As per DaveI, I also make another jumper to connect the "left over" brown/red to the "left over" brown/white to manually connect the headlight control to its power.
I look forward to any advice on this, before I start testing with power - and possibly melting stuff!

HondaMan · « **Reply #6 on:** August 23, 2012, 12:13:14 PM »

Quote from: DaveI on July 24, 2012, 11:55:42 AM

I suppose I did. I'm going to re route it the way you have it and see how that helps.
My goal was just to have the headlight work. It took a while to realize but the headlight power (brown/red) isn't tied into the headlight switch control (brown/white) on these harnesses as it should be. You manually have to do that yourself

You're right about that: I just this week fixed up a 2004 version of this same wiring harness in a K6, and it is also different: I was able to use the Brn/Red (with collar on the wires) circuit to/from the fuseholder by powering it with the Blk/Rd from his K3 headlight ON/OFF switch, which then used the middle fuse for his headlight, and then powered the Brn/Wht in the headlight bucket (for all the other lites) with that same circuit. This puts the taillight load onto the headlight fuse (it goes: Main fuse - ON/OFF hdlite switch - middle fuse - left hand switch - Keyswitch switch contacts - Taillight fuse - Taillight. Whew!) in a convoluted circuit, but it all plugs together with just one male-male jumper in the headlight bucket. Now the taillight is powered thru all 3 fuses!

For those uninitiated: the OEM circuit starts at the 15 amp Main fuse (Red from battery) to the Keyswitch, then becomes Black to the headlight bucket (and voltage regulator). from there, the right hand switch tkes a Black to power stuff, like the coils (Run/Off switch) and the START button, as well as the headlight.

Then:

On bikes with only the START button on the right switch (i.e., headlight goes off during Start), this wire comes back to the headlight bucket as Black/Red or Black/Yellow, depending on which factory made the 750.

On bikes with the OFF/ON switch on the right side, this Black becomes Black/Red (most of the time) on its way back to the headlight bucket.

For either of the above: when installing the PartsNmore harness, this returning wire should go to the middle fuse of your fuseblock. The PartsNmore wires are 2 female connectors on Brn/Red wires with a little white collar on them (the older harness has a red collar instead, so the collar might vary). The returning power from this fuse goes to the Hi/Lo switch on the left handlebar, most often a Brn/Red wire. This comes back from there as Blue and White to power the headlight Hi/Lo beams.

For bikes with the OFF/LO/HI switch, only a Blue and White come back from the right handlebar, and go to the headlight (very simple - K0-K2, CB500, CB550K0 bikes).

HondaMan · « **Reply #7 on:** August 23, 2012, 12:20:52 PM »

Quote from: BrettPPR on August 22, 2012, 03:53:31 PM

I have also just come across this issue on my US K3.
In comparison to the original harness, I find when connecting all EMGO harness headlight connectors, the following 4 wires are "left over".
- brown/white, brown/red, brown, black.
To further confuse issues, the Emgo main harness has two brown/red wires in the headlight, and these have white shrink collars on them?
Are these white collars supposed to mean anything? Are they interchangeable as brown/white?

The Euro bikes before K3 had Brn/Wht going to the middle fuse at the holder, so I suppose this is EMGO's "message" about that?

Quote

As there is only one brown/red wire from the left hand switch block, you have to choose which of the two brown/red harness wires to connect to - leaving the other one "left over"? Does it matter which one you choose?

Technically, they interchange: one of them goes to the left side of the fuse and the other to the right side. I am one of the [anal] few who check with a meter to figure out which is which, and feed power to the left side of the fuse (toward the front of the bike) and use the other side to power things, per the OEM harness.

Quote

From the above comments in this thread, are the following conclusions correct:
1) I do Hondaman's "fix" and make a jumper to connect the "left over" black and brown wires, and then fix the fuses as recommended.
2) As per DaveI, I also make another jumper to connect the "left over" brown/red to the "left over" brown/white to manually connect the headlight control to its power.
I look forward to any advice on this, before I start testing with power - and possibly melting stuff!

On the K3 bike, you may have the ON/OFF switch on the right side? Some did, some not.

If you do, plug the Blk/Red that is the switched ON headlight wire into one of the Brn/Red/Wht Collar wires, and then plug the other Brn/Red/Wht Collar into the Brn/Red that goes to the lefthand HI/LO switch. That will make it like the OEM harness.

If you have only the START button on the right side (later K3), then you have to do the whole "fix".

BrettPPR · « **Reply #8 on:** August 26, 2012, 02:26:01 AM »

Hondaman,
Many thanks for the help on this, and the explanation of Honda logic in the wiring colour sheme.
I am sure it will help me in the future, as I muck around with upgrading a few electrical items.
As my K3 does have an ON/OFF switch on the right hand controls, I followed your advice today and hooked it all up.
All appeared OK, and the big test will come in a week or so (if a chrome plater ever gets some parts back to me?) when I finally get the bike registered and back on the road after many years.

Vcifelli · « **Reply #9 on:** May 26, 2013, 08:06:03 AM »

Hi guys, I was reading through this post as I just rewired my cb750k3. I am new to the forum so not sure if a reply or starting a new thread is best??? I just want to confirm what I did is correct and the leftover wires are ok...

My right hand switch has the start button and headlight on/off switch and the left side has the hi/lo switch. I assume I have the "emgo" harness as I also ended up with the leftover female black, brown, brown/white and brown/red connectors. I just bought it from cb750supply.

Per the previous comments on this thread, I jumped the black to the brown and switched the 5 and 7 amp fuses around. Only the brown/white female remains leftover. Is that correct? The front running lights are now always on (i dont recall if that was the case before rewiring) regardless of whether or not the headlight is on and all lights and signals are operational.

I also have a leftover red female flag type connector coming off the positive battery cable in between the positive battery post and the solenoid. Thick red from batt to solenoid, red/white are both connected but the thin red is free. Any information regarding this leftover red is greatly appreciated???

Thank you, I wouldn't have gotten this far without you guys! - Vince

HondaMan · « **Reply #10 on:** May 27, 2013, 10:31:33 PM »

Quote from: Vcifelli on May 26, 2013, 08:06:03 AM

Hi guys, I was reading through this post as I just rewired my cb750k3. I am new to the forum so not sure if a reply or starting a new thread is best??? I just want to confirm what I did is correct and the leftover wires are ok...

My right hand switch has the start button and headlight on/off switch and the left side has the hi/lo switch. I assume I have the "emgo" harness as I also ended up with the leftover female black, brown, brown/white and brown/red connectors. I just bought it from cb750supply.

Per the previous comments on this thread, I jumped the black to the brown and switched the 5 and 7 amp fuses around. Only the brown/white female remains leftover. Is that correct? The front running lights are now always on (i dont recall if that was the case before rewiring) regardless of whether or not the headlight is on and all lights and signals are operational.

I also have a leftover red female flag type connector coming off the positive battery cable in between the positive battery post and the solenoid. Thick red from batt to solenoid, red/white are both connected but the thin red is free. Any information regarding this leftover red is greatly appreciated???

Thank you, I wouldn't have gotten this far without you guys! - Vince

Usually that Red/White is the one that runs up to the keyswitch? On the K3 early version of the bike, there was both a Red thick wire to the start solenoid and a thin red/white wire with the ring terminal at the battery side that had a bullet connector at the solenoid side. This was where the OEM harness then plugged in the Red/White that went forward to the keyswitch plug under the tank. Later K3 bikes had just the thick red one from the battery to the solenoid, with a Red/Wire pigtail (and bullet connector) hanging out of the black jacket, next to the solenoid, to connect to the Red/White that ran to the keyswitch. This changed to become a Red/White with ring terminal that ran all the way from the keyswitch to the solenoid, where it was paired up with the thick Red one from the battery, right on the solenoid post.

There wasn't really a "right" way to do it, there just seemed to be some way to get the Red/White from the battery (+) to the keyswitch, and it also has to go to the (+) of the rectifier with this same circuit.

Vcifelli · « **Reply #11 on:** May 29, 2013, 04:18:18 PM »

Thanks for the info. She fires up and all accessories seem to be running so I guess it's all good...

The leftover red is part of the battery cable. The old harness was all spliced up and it was used to go back to the key switch it looked like. New harness looks to make the connection through block connectors so like you said as long as its made somewhere it doesn't seem to really matter!

Thanks again -vince

Rick Vessell · « **Reply #12 on:** May 31, 2013, 09:43:31 AM »

HM,

Will this harness work with my 77 550F also? In it's previous life someone had installed a Vetter Windjammer among other things and chopped up the harness pretty good. I have since ditched the fairing and gone back to a standard headlight. I replaced the factory fuseblock with a blade type also. It's running now and most everything works. I have no HI/LO for the light, horn, or left turn indicator on the 'dash' but all running lights and signals work.

Thinking about a rewire along with your upgrade ignition kit.

Thanks,
Rick

HondaMan · « **Reply #13 on:** May 31, 2013, 09:59:38 PM »

Quote from: Rick Vessell on May 31, 2013, 09:43:31 AM

HM,

Will this harness work with my 77 550F also? In it's previous life someone had installed a Vetter Windjammer among other things and chopped up the harness pretty good. I have since ditched the fairing and gone back to a standard headlight. I replaced the factory fuseblock with a blade type also. It's running now and most everything works. I have no HI/LO for the light, horn, or left turn indicator on the 'dash' but all running lights and signals work.

Thinking about a rewire along with your upgrade ignition kit.

Thanks,
Rick

Electrically, they are very similar wiring harnesses. I think you'll have to get creative with the extra lengths, or just get the crimper and some connectors from Del at www.vintageconnections.com and make a professional day of shortening it here and there?

I think you'll find that the horn wires "appear" in an inconvenient place and the arrangement under the seat will require you to either slit away some of the black sheath to reach the regulator and rectifier in the 550. You may wish to dispose of the [dumb] 'safety module' while you're at it, which will simplify several things in the process. This can also be nicely done with the above-mentioned tools. Del also sells the nice vinyl tubing to cover it up if you make your own 'routes'. This stuff will never get hard, either.

Don R · « **Reply #14 on:** June 04, 2013, 08:36:13 PM »

I had forgotten about this issue with the parts n more harness until I rode the K0 after dark the first time and noticed there isn't a taillight. LOL. It works in the park position which is rather curious. I added a 3 fuse block and a hot wire to the headlight bucket for future relays. I'll poke around in the headlight bucket tomorrow and see what I come up with.

HondaMan · « **Reply #15 on:** June 06, 2013, 10:07:02 PM »

Quote from: Don R on June 04, 2013, 08:36:13 PM

I had forgotten about this issue with the parts n more harness until I rode the K0 after dark the first time and noticed there isn't a taillight. LOL. It works in the park position which is rather curious. I added a 3 fuse block and a hot wire to the headlight bucket for future relays. I'll poke around in the headlight bucket tomorrow and see what I come up with.

The harness "breaks into" the taillight wire right in the fuseblock area. The taillight wire comes from the headlight, thru the K0 keyswitch on the Brn & Brn/Wht wires, then thru the "top" fuse (usually 5 amps) in the block, then to the taillight.

The harness presumes that the Brn/Wht wires from the instrument-mounted type switches (K5 and later) has an extra Brn/Wht in the headlight to feed this circuit. So, you may have to create one? If you just tie into the Brn/Wht that comes back from the headlight switch, that should do it.

marc · « **Reply #16 on:** July 29, 2013, 09:13:14 AM »

i am about to tackle the harness in my 1978 750 k with a parts and more harness, does this info pertain to the 77-78 harness also? thanks

HondaMan · « **Reply #17 on:** July 29, 2013, 10:03:44 PM »

Quote from: marc on July 29, 2013, 09:13:14 AM

i am about to tackle the harness in my 1978 750 k with a parts and more harness, does this info pertain to the 77-78 harness also? thanks

The harness will be the least confusing of that fix-up. The Honda wires in the headlight for the turn signals and headlight fuse circuit will probably confuse the daylights out of you, because those bikes were often built with pieces of the CX500 wiring harness up front. One clue: the headlight fuse circuit runs from the "back" side (i.e., the unpressed side) of the START button to the headlight fuse in the fuseholder, but the wire colors might change 3 times in the trip. The wire from the START button is either Blk/Yel or Blk/Red, occasionally Blk/Wht (if 1976 CX500 parts), and it enters the fuse's circuit at the headlight shell, coming back on another wire of the same color. So, you'll see 2 wires for the fuse that are usually Blk/Red, but might also be Brn/Red or Blk/Yel (but there will at least be 2 of them!). Some even have a Brn wire with a little Red collar near the bullet connectors instead, which was the K7 wiring arrangement.

So, try to find out which 2 wires go to the fuseholder for the headlight fuse when you start: this will help.

Tony64 · « **Reply #18 on:** September 30, 2013, 12:10:08 PM »

Hi there ! Can anyone help me with wiring issuses on my cb750 k2 Australia bike? I also have fitted a new parts n more harness and I am having problems with green wire to regulator. When key is in off position the wire is earthed but once I turn key on to start the wire comes alive . All other green wires remain earth except for the one on regulator which I believe runs to field coil ! Any help will be great as I am not that clued up on how this should work

HondaMan · « **Reply #19 on:** September 30, 2013, 09:53:04 PM »

Quote from: Tony64 on September 30, 2013, 12:10:08 PM

Hi there ! Can anyone help me with wiring issuses on my cb750 k2 Australia bike? I also have fitted a new parts n more harness and I am having problems with green wire to regulator. When key is in off position the wire is earthed but once I turn key on to start the wire comes alive . All other green wires remain earth except for the one on regulator which I believe runs to field coil ! Any help will be great as I am not that clued up on how this should work

Wow! That one sounds like a mis-made wire splice in the harness?

Maybe try this: disconnect the Green wire and check with an ohmmeter to any Black wire in the harness. Make sure there is no connection.

In these harnesses, the people are supposed to splice together the Black wires and Green wires to their respective colors up inside the main section of the harness, but perhaps someone goofed? Only Black should test good to other Black, and Green to other Green, as a short circuit. If Black ties to Green anywhere, that would be a dead short to the battery (and fuses) upon power-up. (!)

The Regulator merely supplies power to the field coil as either 7 volts in Medium Charge mode (i.e., when the battery is above 13.2 volts) or as 12 volts in High Charge mode. (They almost never go to No Charge mode, which happens at 14.5 volts, which ties both ends of the Field Coil together and to Ground.) The 12 volts comes from the Black wire on the Regulator, through the regulator's internal contacts, and out the White terminal to the Field Coil. (On some bikes, this White terminal is marked with an "F" for "Field Coil"). The Green terminal on the regulator goes to Ground: on some bikes this terminal is marked "E" for "Earth", most notably Japanese domestic bikes and European versions.

When in "Medium Charge" mode, the White terminal is connected (via the internal regulator contacts) to the resistor on the back of the regulator. The other side of this resistor is connected to the Black terminal, which is 12 volts. This supplies the 7 volts to the field coil to reduce the alternator's output.

These are pretty simple systems.

Tony64 · « **Reply #20 on:** October 20, 2013, 04:03:56 PM »

Thanks to all who helped me out partially hondaman, problem with the green wire that ran from regulator to field coil via 8 pin plug was it was not grounded or connected to any other green wire in harness, when I finally unwrapped wire to investigate it was taped up on very outside of harness as if it was a last minute throw in?? Anyhow added a grounded wire to this wire and fixed the problem! Charging perfectly!

JBCB500 · « **Reply #21 on:** September 20, 2017, 02:56:37 PM »

Resurrecting an old one here!

Hondaman, great info as always. I had exactly the issue you described and I jumped a brown female to a spare black female connector. The taillight, including brake light, now works! Problem is, my turn signals are all on solid.

I also swapped the two fuses as you suggest but this just resulted in me repeatedly blowing the fuse in the 15a slot, so I swapped them back. Everything functions except for the aforemention solid turn signals.

I'm obviously supplying power to them somehow but I don't see an alternative if I only have two black connectors (I've tried jumping from both) and one brown??

News:

Author Topic: CB750 EMGO Wiring Harness solution! (PartsNmore, et al...) (Read 17827 times)