Author Topic: 78 cb750 wiring help on NH seacoast (Read 7682 times)

sethmcalister · « **Reply #25 on:** July 09, 2014, 07:24:12 AM »

Thx, Wilbur. Guess it's time I pick up a multimeter and plug away. I like tinkering, but boy this is frustrating. I'm close to the end and want it on the road...only so much riding time in New England haha!

madmtnmotors · « **Reply #26 on:** July 09, 2014, 11:05:03 AM »

I hear ya Seth. I have refurbished a couple 750 harnesses:

http://forums.sohc4.net/index.php?topic=137351.msg1549191#msg1549191

sethmcalister · « **Reply #27 on:** July 14, 2014, 03:24:11 PM »

Alright so the starter is working... Blew a fuse somehow. But, the GD horn still isn't. Can you guys offer any insight?

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calj737 · « **Reply #28 on:** July 14, 2014, 03:49:08 PM »

Is your left hand control a stock unit, or aftermarket? If aftermarket, it has to be "rigged" to work with the way the stock is set up. One is set to "ground interrupt" the other is set to "pass 12v to horn".

Stock switch is a ground interrupt. I'm betting your aftermarket is reversed as was mine. I had to run a jumper to headlight so that pressing the horn button, actually "grounded" it, but as I have it, headlight must be burning for horn to work.

sethmcalister · « **Reply #29 on:** July 14, 2014, 04:03:33 PM »

The controls are stock. The PO had the light green that goes into the control attached to the gotten and the ground. The wiring schematic calls for light green and black. Neither combination works for me though. What is a ground interrupt?

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calj737 · « **Reply #30 on:** July 14, 2014, 04:31:29 PM »

Means that it has power always, but depressing the button "grounds" the switch, thereby sounding the horn. If you're using a stock control, and a stock horn, then the wiring follows stock.

On my 550 diagram, the green from the switch also runs to the horn. This is a ground wire. The black at the horn is power. The handle switch is also directly grounded. Is this how yours is wired currently?

sethmcalister · « **Reply #31 on:** July 14, 2014, 04:36:27 PM »

Yes, the green from the switch runs to the horn. I don't know if the switch is grounded. However, based on what you're describing, it is the same setup.

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calj737 · « **Reply #32 on:** July 14, 2014, 04:37:56 PM »

So there needs to be a black at the horn too. That's the "power". It can be tapped from the ignition switch, or the stop/run switch. 12v switched source...

sethmcalister · « **Reply #33 on:** July 14, 2014, 04:53:19 PM »

There is a black at the horn.

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calj737 · « **Reply #34 on:** July 14, 2014, 04:58:27 PM »

And can you verify that the black has 12v to it? Should be when key is "On"

sethmcalister · « **Reply #35 on:** July 14, 2014, 05:19:48 PM »

I have not tested that. Should be red multimeter to black and black multimeter to green, right?

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calj737 · « **Reply #36 on:** July 14, 2014, 05:36:55 PM »

Black probe to any ground, or ground wire.

sethmcalister · « **Reply #37 on:** July 14, 2014, 05:37:51 PM »

Okay, I will check that first thing tomorrow.

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sethmcalister · « **Reply #38 on:** July 15, 2014, 03:26:08 PM »

Checked the black... It has 10.43v to it. Do you think it just isn't putting enough power out to it for it to run?

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calj737 · « **Reply #39 on:** July 15, 2014, 04:26:52 PM »

That is suspicious... I don't think 10.4v will turn the starter. It would be symptomatic of a very weak battery. Can you double-check yours? Btw, heading out for dinner with my bride to celebrate 20 years, so I'll be offline shortly for the night.

I'd check battery, making sure it shows 12.+v. Then trace where you lose that voltage to black wire. If battery is low, charge it fully. Then retest black with key on. Don't leave ignition on for long, as it will drop quickly-

sethmcalister · « **Reply #40 on:** July 15, 2014, 04:33:02 PM »

I checked the battery yesterday and it was at about 12+v, but definitely below 12.8v (can't remember exactly what it was off the top of my head). It is brand new but I haven't been able to start the bike long enough to charge it. I'm guessing you'll suggest that I charge it? I don't normally run the starter and just kick it...or have when I had it running twice. I'll hook the battery up to the charger overnight and see how it goes tomorrow.

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sethmcalister · « **Reply #41 on:** July 15, 2014, 04:33:10 PM »

Congrats by the way!

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calj737 · « **Reply #42 on:** July 15, 2014, 08:01:03 PM »

Thanks. As it is, 12+ is fine. So when you turn the key, headlight is on and black wire measures 10v? That's a little low, though not impossible. And for a kick-over, it should have enough juice.

I need a refresher-
You've checked that the clutch safety switch is good or removed?
You're kicking it, so no solenoid, and you're getting power beyond the Start/Run switch?
If you do push the START button, anything?

Sorry, we've been going on so long, I can't recall all the details.

sethmcalister · « **Reply #43 on:** July 16, 2014, 04:39:06 AM »

I have not checked the clutch safety switch, where do I find it? The solenoid and starter do work, but I don't believe I've had enough juice to start it with the starter.

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calj737 · « **Reply #44 on:** July 16, 2014, 04:59:59 AM »

Should be a Green and Grn/Red wire coming from the left hand control. The green runs to L front indicator. The Grn/Red works it's way to sub harness connector, then off to Start Safety motor via the Stop/Run switch.

Can you use an auxiliary battery to supplement the charge to use the electric starter? If you use a car, don't have the car running! Just tap the battery. When running, car alternators put out way too much current for your bike's system to handle and you'll cook the electrics $:-\$

sethmcalister · « **Reply #45 on:** July 16, 2014, 09:11:47 AM »

The clutch safety switch works as far as I know. Without the clutch engaged it will not start. I charged the battery all last night so will check the voltage when I get home....but, my tank isn't back from the body guy yet. I can hook up the 550 tank for now just to get it started.

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sethmcalister · « **Reply #46 on:** July 16, 2014, 04:45:16 PM »

So battery is up to 13.5v and the black horn wire is at 11.3v. Should be enough to power the horn, right?

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calj737 · « **Reply #47 on:** July 16, 2014, 05:47:39 PM »

More than enough

sethmcalister · « **Reply #48 on:** July 16, 2014, 06:06:05 PM »

Alright.....so then the switch is bad? Or is there a problem with the light green ground interrupter?

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calj737 · « **Reply #49 on:** July 16, 2014, 06:59:16 PM »

To verify, run a jumper from battery + to horn! and ground from horn to frame. If it sounds, then you have a switch problem, or a wiring problem from the switch. I'd suspect switch at this point, but verify the jumpers do actually sound the horn.

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Author Topic: 78 cb750 wiring help on NH seacoast (Read 7682 times)