Topic: Biting off more than I can chew (1977 cb750)

[Floshenbarnical]

Finally time to un-screw the cobbled-together mess of a wiring harness the previous owner put in.

It’s a horrible tangle of harbor freight crimp connections. I have many spools of wire, and many vintage connectors. I have many wiring diagrams for this bike, but because the only stock electronic unit left is the headlight, and the other lights are LEDs, most of the wiring harnesses aren’t super helpful.

The coils/ points/ ignition system is all good to go thanks to Hondaman. Sadly the rest of it needs to get done now.

I did a bad job when I disassembled the harness so about 75% of it is flagged etc, and the rest is going to be trial and error.

If I post exhaustive pictures of my equipment, etc, would any of you be willing to help me figure out the correct way to do this? I’m a little lost.i need to wire up a headlight, 4 turn signals total, and a brake light and a stop light.

[Floshenbarnical]

See if this helps, it’s as simple a diagram as there is.

Thanks for this. I downloaded it ages ago but my pc broke down and I lost it. The only thing that complicates things are 1) I don’t have a starter 2) I am using Hondamans ignition. I’m sure I’ll figure it out though.

[Floshenbarnical]

I’ll bear that in mind when I take care of that.

Another issue: all the reg/rec diagrams have 5 wires. Mine has 7. It’s one of Rick’s. Not sure where the extra wires go!

[BenelliSEI]

Originally the regulator and rectifier were two devices. Your single unit has more as it does both jobs. It should have that many…..

[Floshenbarnical]

I’ll bear that in mind when I take care of that.

Another issue: all the reg/rec diagrams have 5 wires. Mine has 7. It’s one of Rick’s. Not sure where the extra wires go!

There are 2 separate GREEN wires and each needs its own ground. One is for the Rectifier, the other for the Regulator. The 3 yellows are for the Stator, the WHITE is for the field coil, the RED (or BLACK) is for 12v reference from the battery (don’t connect that directly to the battery, use a switched circuit else the field coil is constantly powered and your battery will drain).

You mean a switched circuit like a key switch?

Thanks for the help everyone. I have the charging system mocked up and ready to be pretty. Stupid accessories are still kind of a basket case. Not sure whether or not to hook up the power and start plugging the last few connections randomly until something happens, or whether to start from scratch. Depends how hard it is to figure out I suppose.

[Floshenbarnical]

Yes, switched by the key.

Like this?

Ricks haven’t made my reg-rec in 10 years so the man on the phone drew a diagram:

[HondaMan]

Yes, switched by the key.

Like this?

Ricks haven’t made my reg-rec in 10 years so the man on the phone drew a diagram:

That Reg-Rec's Blue wire should be able to attach then to any Black wire available. The OEM regulator had one terminal for Black, one for Green Ground, and the last one was for the field coil.

[Floshenbarnical]

Is the circled item just a connector?

[newday777]

Is the circled item just a connector?

No.
It's a starter solenoid
Click on the picture and enlarge to see the words, starter solenoid

[Floshenbarnical]

Going ti try to start the bike tomorrow. Quick question though: I have hondaman’s ignition but I’m suddenly paranoid I wired the points back to front. They’re inside heat shrink so I can’t see. What will happen if I start it and they’re connected wrong?

[Floshenbarnical]

It won’t start as the firing order is backwards. Easy enough to reverse afterwards.

Ok. As long as it’s not going to fry anything. I left the connections open to make it easier to switch before protecting them with heat-shrink tubing.

Another thing that occurs to me: my current turn signal for my rear system has a wire for the left and a wire for the right indicator. That’s fine for the indicators in my bars, but my rear unit is a single piece that incorporates both left and right turn signals and only has a single + wire and a ground wire. How do I figure this out?

[BenelliSEI]

Left and right turn signals are definitely fed by two different (+) wires. Front and back.

[Floshenbarnical]

Left and right turn signals are definitely fed by two different (+) wires. Front and back.

Unless you install a diode for the rear turn signal isolating the R+ from the L+. So that may be your requirement, but I’d really want to see the fixture and any wiring instructions that came with it.

Of course. Here is a picture of the unit. Red is running light. Black is ground. Blue is brake light. Yellow is turn signal.

[HondaMan]

Your Transistor Ignition has a Lifetime Warranty, too! Just let me know if it breaks, I'll swap you for another one.

[Floshenbarnical]

Well, you guys are all brilliant and I’m a fool - this is a unit of TWO that are supposed to be installed side by side

I performed a simple test by simply touching leads to the battery. Black is ground, red is TAIL, blue is HIGH and yellow is turn. Yellow only lights up one side of the LED strip, and I expected it to light turn signals on each side.

I recalled that I had received two when I ordered it, and found it in my box O supplies. I then recalled that I had been like “oh, bonus! They sent me a dupe!” whereas in actual fact I couldn’t read the website properly.

Luckily I haven’t drilled the slit for it yet so I’ll just install both! They each get their own TURN lead for left and for right! It affects the aesthetics a little but a blessing is that it’ll be twice as bright. And good grief they’re bright already for such little lights.

[Floshenbarnical]

Honestly having looked at some wiring diagrams, the instructions for the equipment, and learning some basic principles about electrical systems, I’m pretty confident I can throw out all his work and do it much better and simpler myself. I think the reason it’s such a complicated mess is because he has tried to force the stock wiring design onto the equipment he purchased instead of slightly modifying the equipment and imagining a new diagram. I’m specifically talking about the lighting, inc. dash lights.

Edit: figured it out. Accidentally stayed up until 2am drawing the entire diagram for my bike and all its equipment. Then I tested all the lighting circuits in an online tester and it all works! Time to get soldering!

[Floshenbarnical]

You’re right, I got the words mixed up but the principles are the same.

Ok, my headlights are incandescent but my indicator for the high beam is LED. I have a 3-way switc, Off Lo and Hi positions. Main Beam IN, Hi and Lo OUT. Indicator has a positive and negative wire. Does anyone want to sketch a diagram for me? I have some extra diodes I can use if they are needed. I’m easily able to adapt wiring diagrams I see but LEDs are throwing me off. These circuits have diodes going into LEDs sometimes but not always. Not sure what the rule is.

[Floshenbarnical]

Great. For some reason he has to positive leads and two diodes going into the Hi light.

So if all the lights inc. the backlights on the gauges are LED, would all of them need their own diode? It sort of looks like he has run the + connection for all the LEDs except the turn signal  through diodes and then split them off and grounded each LED. I mean, it worked

[Floshenbarnical]

The only diodes you’d probably need are for the turn signals. Often the LED allows power to “bleed” through and when you activate the R, the L also flickers. So with a diode, that stops that from occurring.

As for the dash lights, if they share the same common power feed, you could run into the same problem. Wire things up and give it a test to know for certain.

I guess he was either being careful or was guessing. All the dash lights inc the backlights have separate power in/outputs and the circuit I have drawn seems to eliminate the need for them.

I tested the full turn signal circuit today on the bike with stretchy  crocodile leads and it all worked, so that’s good. Time to do the headlight circuit.

[Floshenbarnical]

Just in case anyone is curious, this is what the bike looks like now

[spotty]

Subscribed as I may need to use some of this info when nine gets to the wiring stage

[Floshenbarnical]

Neat looking, but those clip ons are awfully low! Make my back hurt just looking them… and I think you might need to do something with the exhaust. It’s length will not help that bike run well.

This was my riding position last summer, and due to a bizarre coincidence with the same of my body it’s actually very comfortable! I hear you though.

You are correct about the exhaust - it was always a temporary solution to get around the lowered sump. It gets in the way of the collector for the 4:1. So I have 2 options: buy delkevic headers and have a shop modify them to fit, or buy Carpy’s “Sidewinder” exhaust system that goes around the sump under the right frame rail.

Not sure what to do.

[Floshenbarnical]

Q: do I need extra resistors in a simple circuit involving one LED, a switch, a flasher relay, and a battery? I’m trying to figure out if my flasher relay is broken using a simple circuit. The LED just stays on. I suspect I have damaged it by connecting it backwards because I have the same issue both ways - it just stays lit and doesn’t flash.

Or perhaps 1 led isn’t enough resistance to activate the relay? I’ll connect all 4 up and see

[Floshenbarnical]

LEDs often require a different type of flasher. The stock unit needs the engine to be running to activate the lights.

What flasher are you running, have you tested it with the engine running, and how do you have it wired up???

This is the same relay that came with the bike. The previous owner already did LED turn signals, but may have used some of the aforementioned diodes to trick it into working if it’s not an electronic flasher. I suspect it may be a thermal flasher.

Edit: I did some sleuthing and it’s a thermal flasher. Got an electronic one arriving Friday.

[Floshenbarnical]

Everything going well. Brake, tail, turns, license plate and gauge backlights ready to go.

My low headlight bulb burned out though. It looks like it’s the original sealed headlight. Main beam work.

Does anyone know of an affordable beam I could plug in there?it’s the OEM shell and rim