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Thread: Wiring issues

  1. #1
    CB750 New Member Dylan438's Avatar
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    Wiring issues

    I have a 1976 Honda CB750F. Iíve done some research on the electrical issues Iím having and am having no luck. My Speedo and tach lights are not running, and neither is my running tail light. The tail light will turn on when in ďparkĒ, and brake lights work just fine. Would really appreciate some help!

  2. #2
    CB750 Member jimmbo62's Avatar
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    Have you found out anything? I also have a 76 Cb750F and am having the same problem. Mine started when I had to disconnect everything in the headlight bucket. After reconnecting everything, I went from no electricity to then I managed to get to the point where you are. I went thorough all the connections and then somehow I lost the instrument panel lights as well. I checked the right hand control switch and all was fine there. I checked the ignition switch and it looks a little suspect. I took it apart and cleaned it up, checked the continuity, connections and changed the springs in it. I hooked up my voltage meter to the positive and then tested each fuse with the red and only had electricity to the tail light. (I rebuilt the fuse box and put in a modern one).... I still think it is the ignition switch for some reason. Maybe it could be the same with you? ...also, in the headlight bucket I have an extra green/red wire that I can't figure out where to connect it to. It's not on any wiring diagrams.

  3. #3
    Moderator dirtdigger's Avatar
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    Green with a red is neutral safety light and starter neutral safety. Get a good factory honda wiring diagram. If it all started when you disconnected everything then it is a problem with the reconnections. I would take it all back apart and start over with a GOOD diagram on hand. Dont just match colors back together and think everything will be good, follow the diagram ONE circuit at a time.

  4. #4
    CB750 Member jimmbo62's Avatar
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    Quote Originally Posted by dirtdigger View Post
    Green with a red is neutral safety light and starter neutral safety. Get a good factory honda wiring diagram. If it all started when you disconnected everything then it is a problem with the reconnections. I would take it all back apart and start over with a GOOD diagram on hand. Dont just match colors back together and think everything will be good, follow the diagram ONE circuit at a time.
    Thanks... I think I have a pretty good diagram although hard to find a good one for a 76 cb750F Euro and I did go through all the circuits and traced the wires. It was all working fine and suddenly things went wrong again. I did read that the green/red was for neutral starter safety but can't figure out what should connect to it. It's a female connection and is hot. There was a lot of mickey mouse stuff going on in the bucket that I thought I had cleaned up and corrected.... Ofcourse I'm sure I have probably made a mistake somewhere as I didn't mark the wires good enough before disconnecting them and the pictures I took aren't good enough.... I tried by reading through every thread I could find in every forum so I haven't asked for any help. I now have the wiring diagram in my head along with every wire on my bike lol.... I appreciate your comment and any further help or comment. I'm hoping to see if Dylan438 finds out anything since he has a similar problem...Anyway, I'll look for a better wiring diagram and go through go it all one circuit at a time again... another thing is that when I moved the wires leading to the console lights the neutral and oil indicators quit working while the turn signals still work. They haven't worked in the "park" position since I started messing with everything.

  5. #5
    CB750 Member jimmbo62's Avatar
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    I went through everything again. I changed out a few of the wire ends/connectors. It seems like I have it exactly like on the wiring diagram but of course I could have missed something. I still haven't figured out what the red and green wire goes to and the clutch safety mechanism is functioning. Everything works fine now but still no headlight, speedometer and tachometer lights. The right hand controller is only about a year old. Start button and kill switches work. Any idea of what it could be? There doesn't seem to be any electricty to the headlight except the pilot light works when in park... I made a bridge from black to brown white and then the front running lights works but only on the left side. I took that off again. My bike is a European model and all this started when I converted over to US signal lights (no running lights in the euro model if I'm not mistaken) ...Sorry to jump this thread, I thought maybe since we have a similar problem that we could help each other out.

  6. #6
    CB750 Guru amc49's Avatar
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    It's deadly obvious skills are playing a big part here along with likely whacky wired switches that do not follow the Honda color code protocols. The bikes in and of themselves are stupid simple to wire and why I don't jump in, I get frustrated doing wiring over the net as it requires too much patience once ALL the circuits are suspect and knowing how easy they are to wire I don't have much of that. People do NOT know the critical things to mention to get the issues fixed quick and the loss of communication kills getting it done. Wiring correctness lies in EVERY detail and why so much trouble, the most irritating part of all is knowing that I personally could fix most of these issues in maybe 20 minutes and even with mismatched wiring colors if I were there personally to survey the EXACT situation with all its' gory details.

    I don't even have color coding on the GM HEI ignition modules I subbed for the OEM Honda ignitors on my DOHC, I used the same red wiring on every circuit, that's a big handful of wires there. All the electrical cares about is being connected right, it could care less what color the wires are.

    Dirtdigger has it right..........................'follow the diagram ONE circuit at a time.' If you can't do that you are not capable of doing the job. Not trying to be mean at all, just the truth of it.

  7. #7
    CB750 Guru amc49's Avatar
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    'It was all working fine and suddenly things went wrong again.'

    Stuff like that is worthless and why mention it? We don't believe in magic and neither should you.

    'I still haven't figured out what the red and green wire goes to and the clutch safety mechanism is functioning.'

    If you CAN read the schematic you would already know the clutch side of that circuit can be working yet still have something unconnected. You should be able to see pretty quick what is not connected up too, the US schematic shows it has THREE ends to it.

    Things like this.......

    '...while the turn signals still work. They haven't worked in the "park" position since I started messing with everything.'

    ...are what I'm talking about, the schematic if US version clearly shows that the taillight ONLY is the only thing that lights up in 'park'. So, more error..........

  8. #8
    CB750 Member jimmbo62's Avatar
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    That is exactly why I avoided posting until this thread came up... I worked on this about 10 days and now feel I have the whole wiring diagram in my to correspond with each wire. It was a mess and I'm learning so much and how simple the wiring seems to be. I'm just missing something. After Dirdigger's response, I read through the manual again, looked at another schematic. That's where I found that while in Park nothing should work except the pilot light and taillight. (everything worked in Park when I first bought the bike). I've removed so many extra wires from the bucket now and it's cleaned up and looking more like it should. I've come this far on my own and I'm sure all figure it out even if it takes me 10 more days...

  9. #9
    CB750 Guru amc49's Avatar
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    ' I'm just missing something.'

    As long as you can keep looking at it like that you will eventually find the problem. Questioning of yourself is the most important tool in your toolbox yet most have never seen that tool.

    I have never paid ever for a car or bike repair and I now can fix electronic cars as well as electronically controlled automatic transmissions and with zero formal training in any of it. It comes from reading, thinking, and always suspecting your possible self error or simple lack of knowledge in whatever you are working on. The people who assemble this stuff are absolutely no smarter than you and that makes it then a matter of you getting the lacking skills. I have always been able to find the source of all troubles; sometimes it takes a while but I made up my mind NOT to throw parts at at things like when I was in car parts I saw so many people do to waste thousands of dollars. Careful thinking is worth spending time on as it makes $$$$$$$$$ come out of thin air but it seems to be a lost art, everybody is in too much of a hurry now and the problem.

    I most certainly mean no disrespect at anybody posting this stuff but the air needs to be cleared of the bullsh-t from time to time. Doing electrical over the net is one of the harder things to do once it goes beyond one or two wires.

    FYI, in my younger days I had an AMC Hornet, a pretty rare one with the 360 inch V8 in it. The car had an issue to where it would suddenly run a new battery down to then not do it again for a month or so. I chased that issue for several months in bits and pieces and finally it p-ssed me off enough I literally started at the front and went through entire wiring harness, and during that time began training myself on power leak detection by yanking fuses to see which major circuit is leaking power at rest. I traced the issue to the new-at-the-time seat belt detection module, which had some kind of a power short inside that did not leak at all times, only when it wanted to. I yanked the module and rewired around it to make car start again and the problem disappeared forever.

    Sometimes it takes a while depending on where your head is that day and how receptive it is to thinking out of the box that day.
    Last edited by amc49; 03-28-2018 at 04:28 AM.

  10. #10
    CB750 Guru amc49's Avatar
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    At the risk of making a fool of myself I went through several schematics and it appears that Honda pretty much has all wiring in the back of headlight all insert same wire color into same wire color EXCEPT for supplying main power to the lighting system. The power comes off the multiplug black connector and either a brown/white or brown/blue (F bike) plugs into the black connector to pick up lighting power. Obviously if an aftermarket lighting switch one will have to determine any color error there and correct for that.

  11. #11
    CB750 Member jimmbo62's Avatar
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    Funny about the Hornet. My highschool buddy had one too. My dad died when I was 14 and I got his 65 Ford F100. I was alone and learned how to fix everything myself. Anything I could take apart I could put back together and I had a good ear for finding the problem. I learned fast that a bum starter didn't mean I needed a new one but could change the brushes out or whatever. Borrowed a forklift from work and changed out the whole front end when I was 16 after my brother took the truck and totalled it...I started out with this wiring crap knowing it could be a nightmare. I've gone through so many threads from so many forums. I have gone through countless wiring diagrams. I feel I'm coming around and understanding things better now that I've dived in to the point of no return... When I was married I hated when my wife would call for help with her computer or our satellite dish and understand that this would be about the same for you. So, I was taken a little back but no harm no foul. I can take it and what you wrote makes total sense. I'm just human and am always hoping for a quick fix or shortcut. Actually I'm proud of myself that I've come this far and so glad about how much I've learned and am still learning. I'll get this. It's just a puzzle piece I'm not seeing. I've changed so much after the previous owner now...There is another set of connections before the headlight bucket that I'll go through again. I know where each wire should lead to and what it's for except for the extra wires from the Honda factory that are there but on no diagrams I can see.

  12. #12
    CB750 Member jimmbo62's Avatar
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    Quote Originally Posted by amc49 View Post
    At the risk of making a fool of myself I went through several schematics and it appears that Honda pretty much has all wiring in the back of headlight all insert same wire color into same wire color EXCEPT for supplying main power to the lighting system. The power comes off the multiplug black connector and either a brown/white or brown/blue (F bike) plugs into the black connector to pick up lighting power. Obviously if an aftermarket lighting switch one will have to determine any color error there and correct for that.
    Yes, I thought I corrected that when I put in the new right hand side control switch.Anyway, I'm soooo close I can almost taste victory!

  13. #13
    CB750 Guru amc49's Avatar
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    'Actually I'm proud of myself that I've come this far and so glad about how much I've learned and am still learning.

    Great job and never stop, the technology keeps on coming and the losers fall behind that and most of the problem.

    Me? Well, this thread shows I have things to work on as well. I can only ask for forgiveness over my lack of patience. I clearly do not understand what it takes to arrive at a same conclusion slower than I do. Making me totally full of sh-t at times.

  14. #14
    CB750 Member jimmbo62's Avatar
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    Quote Originally Posted by amc49 View Post
    'Actually I'm proud of myself that I've come this far and so glad about how much I've learned and am still learning.

    Great job and never stop, the technology keeps on coming and the losers fall behind that and most of the problem.

    Me? Well, this thread shows I have things to work on as well. I can only ask for forgiveness over my lack of patience. I clearly do not understand what it takes to arrive at a same conclusion slower than I do. Making me totally full of sh-t at times.
    LOL! It's all good and from what I've seen in the majority of posts on electrical issues, totally understandable. And at my level, I didn't really express myself very well.

    Sent from my SM-G950F using Tapatalk

  15. #15
    CB750 Member jimmbo62's Avatar
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    well shit. I got the headlight to work. In the connection box before the headlight I switched a blk/wht to blk/wht to blkwht/to blk/wht to blk /yellow and vice versa. Got all excited because the headlight and everything worked.... But forgot to check the horn... Aand, the Hi/Lo on the right hand switch doesn't do shit... to be honest, I don't know if it ever did. The high and low beam switch works fine on the left hand controller. Maybe I have the wrong right hand controller switch. Anyway, for now I just squeezed the horn connector into the same connector as the headlight is in and now everything works. I'm not stopping there though. I WILL get everything to work like it's supposed to eventually. Maybe just buy a right hand control switch for a fricken 75 if I have to... I'm getting close... If anyone cares...haven't heard much from the original poster anyway... Going crazy and talking to myself LOL...
    Last edited by jimmbo62; 03-30-2018 at 03:15 PM.

  16. #16
    CB750 Enthusiast raywilson's Avatar
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    I'm Ray Wilson who has "taillight woes" posted about the same time you did. I still have no taillight. The brown and the brown w white still have no current. I have power at the fuse via a jumper from the 4 wire black connector to the brown w blue wire that goes to the fuse block. Absolutely everything works except the tach n speedo lights and taillight. There has to be some funky connection in the mess under /around the battery. I have a new starter solenoid which I think is part of the electric sharing system. I haven't memorized that part of the diagram yet. I've thrown in the towel a couple times now but I can't find any mobile mechanics to come look. Taking it to a shop would relegate it to 6 months of sitting gathering dust. Clymer's has a great colored wiring diagram. I pretty sure someone who is talented with a meter could figure it out in less than an hour.

    Sent from my SM-G930V using Tapatalk

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