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

[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.

[calj737]

Just to the dash indicator HI into the headlight HI wire. Then when the light is switched to HI, the indicator will illuminate. The bulb for the dash ground terminates to the frame anywhere.

[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

[calj737]

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.

[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

[calj737]

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.

[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

[calj737]

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???

[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.

[calj737]

Diodes have no effect on causing the flasher to excite, only preventing the power bleed across to the other side.

[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

[spotty]

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

go to ebay and get a modern 7" lens/reflector that takes a H4 halogen, much better light for the same electrical draw, just make sure it isn't one with a plastic lens, the H4 WILL melt it, or get a full LED unit that will go straight into your stock rim/bucket

[Floshenbarnical]

On DSS I found an after market h4 unit that comes with the bulb. It’s a plug n play for the cb750.

Is it going to melt my switch? Do I need a relay to be safe? It’s a 55/60w h4 bulb (removable)

[spotty]

On DSS I found an after market h4 unit that comes with the bulb. It’s a plug n play for the cb750.

Is it going to melt my switch? Do I need a relay to be safe? It’s a 55/60w h4 bulb (removable)

i used to have a 90/110 in my 750 back in the 90's and nothing fried

[tctreppin]

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!

Once I bought the “Combination regulator Rectifier I bought one for EVERY 750 since!!
 Super easy to wire if u go that route I ll draw you a picture AND U WONT HAVE TO FIDDLE WITH SOME 50 yr old tech


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[tctreppin]

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:

Excatly


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[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:

Excatly


Sent from my iPhone using Tapatalk

Thanks, brother