Topic: Weird, relentless, cb750 starter button/wiring issues

[cshanek]

Greetings SOHC friends,

I have a 76 cb750 that a friend gave me last year. I replaced the entire wiring loom (it had a major short), rectifier, ignition switch, and handle bar switches this year. I bought both handlebar switches from VintageCB750 (http://www.vintagecb750.com/products/5/electrical/90/handlebar-switches). I also have a nice 73 CB500 that I rewired at the same time (and installed the same switches). So now down to the problem. I have wired, rewired, checked connections, checked diagrams, tested, and rewired, and for the friggin life of me I cannot get any action out of the starter button. I spent so much time on this that I actually assumed the switch was bad and sent it in for another, and whalla, same problem. Everything else works (though the winker isn't blinking either which is weird, and I am 99.9% sure the winker is fine. I can kick start the bike just fine and she purs like a kitten. I can also run the starter solenoid connections to the battery and the starter moto immediately turns. So my questions to you, the salty, savvy SOHC masses are:

How do I narrow down the problem? Should I run alligator clamps across the 2 sets of wires for the started switch assembly to bridge the "on" and "run" switches in case they are never engaging? Should I hook up my multi-meter to the rats nest (currently exposed) where the switch connects and look for power when I hit the start button? I am almost out of ideas here. I would use some of my older switches (which worked) for testing, but the soldered piece inside became detached, and apparently my shotty soldering job didn't fix it that well.

I will post rats nets pictures also if that helps. it is getting late in the season here in CO, and I just want to ride my bike.

[Desert-SOHC]

From what I can tell from the wire diagram, the switch grounds the solenoid for the starter.  I would say bad ground at the handle bars.  Take the switch apart and scrape the paint off where it contacts the bars and see what happens.  Had the same thing happen with my horn switch, and that was the issue.

But I'm a K8 guy and mine is a completely different wiring setup

[Keith]

Clutch needs to be pulled on later models...Bad switch?

[my name is nobody]

The 76 k6 has the headlite off during cranking feature. The wiring harness and controls are different and exclusive from any years before or after, (I think).... Your harness and controls are correct for the k6?

[Jerry Rxman Griffin aka MuthaF'er]

Clutch safety?

[PeWe]

Clutch needs to be pulled on later models...Bad switch?

Easy to miss that small switch and its wiring into the headlight bucket. This is when the neutral switch  does not indicate neutral so the bike can be started with gear in as long as the clutch is used. Neutral lamp is lit when gear is in neautral?

[ekpent]

The 76 k6 has the headlite off during cranking feature. The wiring harness and controls are different and exclusive from any years before or after, (I think).... Your harness and controls are correct for the k6?

The 1976 F model 750 has that headlight feature but I do not believe the K model 1976 does.

[cshanek]

From what I can tell from the wire diagram, the switch grounds the solenoid for the starter.  I would say bad ground at the handle bars.  Take the switch apart and scrape the paint off where it contacts the bars and see what happens.  Had the same thing happen with my horn switch, and that was the issue.

But I'm a K8 guy and mine is a completely different wiring setup

I will take a look, though the would have been a problem on the new switch I initially got, and its replacement.

[cshanek]

The 76 k6 has the headlite off during cranking feature. The wiring harness and controls are different and exclusive from any years before or after, (I think).... Your harness and controls are correct for the k6?

I ordered them specifically for my bike (year, make, model, K6) from a place that only sells parts for old 750's so I assuming that is all fine.

[cshanek]

Interesting. I road this bike around a few times last year before rewiring it and I don't remember the clutch feature though I might have forgotten that from continually using my 73 500. I will run home and test this tonight. Seeing that I have spent about 2-4 hours testing parts (replacing them from my working 500), and continuity, I will feel like a complete idiot if this works.

[magnum56]

Interesting. I road this bike around a few times last year before rewiring it and I don't remember the clutch feature though I might have forgotten that from continually using my 73 500. I will run home and test this tonight. Seeing that I have spent about 2-4 hours testing parts (replacing them from my working 500), and continuity, I will feel like a complete idiot if this works.

You're not a complete idiot ... unless you give up !

Patience grasshopper.     

[cshanek]

UPDATE ....

So the #$%*ing nightmare continues. I again rewired and tested everything tonight, and the following were my takeaways:


• It is not a neutral issue. The bike was in neutral, and neutral indicator light was on when I attempted to start. I also tried engaging the clutch, and tried in gear as well
• The battery is charged and happy
• The coils get hot when the ignition is on
• Other than the indicator lamps, the brake light, and the horn, absolutely nothing happens when the ignition is in the middle position. Tail light is not on, though front light was.
• When the ignition switch is in the full-on position (what the hell is this position called?) the indicator lamps, the brake light, and the horn works. The turn signals are solid when switched, and the headlamp and taillight worked
• There are a couple of connectors that aren't being used (don't match with anything). A blue brown connector to the buzzer on the fork, and a brown/red connector from the harness.
• I tried another ignition switch (the original) and that didn't change a damn thing, so perhaps I have narrowed it down to everything else electrical on the bike.
• At this point I am thinking long and hard about taking the #$%*er in somewhere. I have spent a ton of time on this and at some point of time or another replaced the whole harness, ignition switches, solenoid, rectifier, fuse box/assembly, handlebar switches, turn signals, and headlamp.

[HondaMan]

UPDATE ....

So the #$%*ing nightmare continues. I again rewired and tested everything tonight, and the following were my takeaways:


• It is not a neutral issue. The bike was in neutral, and neutral indicator light was on when I attempted to start. I also tried engaging the clutch, and tried in gear as well
• The battery is charged and happy
• The coils get hot when the ignition is on
• Other than the indicator lamps, the brake light, and the horn, absolutely nothing happens when the ignition is in the middle position. Tail light is not on, though front light was.
• When the ignition switch is in the full-on position (what the hell is this position called?) the indicator lamps, the brake light, and the horn works. The turn signals are solid when switched, and the headlamp and taillight worked
• There are a couple of connectors that aren't being used (don't match with anything). A blue brown connector to the buzzer on the fork, and a brown/red connector from the harness.
• I tried another ignition switch (the original) and that didn't change a damn thing, so perhaps I have narrowed it down to everything else electrical on the bike.
• At this point I am thinking long and hard about taking the #$%*er in somewhere. I have spent a ton of time on this and at some point of time or another replaced the whole harness, ignition switches, solenoid, rectifier, fuse box/assembly, handlebar switches, turn signals, and headlamp.

This sounds like bad fuseholder clips. VERY common.
Disconnect the battery (at least the (+) terminal) and/or unplug the fuseholder from the main harness. Remove teh fuses and take a small penknife and scrape the insides of the fuse clips. If they are dark (and probably are), the chromate has let go of the metal clip and is acting as an insulator. This can heat up and melt fuses, or it can prevent them from passing current at all. That's why I started making the ATC Blade fuseholders for these bikes. Also, the glass fuses (SFE automotive type) have not been made since the late 1990s, so any fuse you have in it today will not survive road shocks very long, and will fail while riding. The glass fuses we can get today are not shock-rated: they are merely instrument fuses.

The keyswitch may also be a problem, if you have not replaced it, or if it is the EMGO replacement switches commonly (and incorrectly) sold as the switch for this bike. The EMGO switch can only carry about 8 amps, and the 750 uses 12 amps when the lights are on. This destroys the EMGO switches, often by melting the wires right off the back of the switch! Mine did it on I-25, just north of Centennial airport, in morning rush-hour traffic at 75 MPH.

[cshanek]

I tested the ignition switch tonight (it is new), with the original and the behavior didn't change. the fuse box is also new (because the connectors had broken off the original box) so I replaced that as well earlier in the year (along with handlebar switches, loom, rectifier, solenoid, winker, and turn signals).

[Gene]

The brown/red goes somewhere and should be used, but I don't have a diagram in front of me. The buzzer lead should be taped off so it doesn't ground out.

When you replaced the harness were you sure to make the ground to bare metal on the frame? Forgive me if you've already stated that.

[cshanek]

On second question, I have not stated that, but yes there is a ground on the left side I believe on the frame behind the side cover. It is pretty large. Not necessarily apples to apples but I redid my 73 500 at the same time, and though I am having charging issues currently, everything else seems to work great, and the are very similar.

[Gene]

On second question, I have not stated that, but yes there is a ground on the left side I believe on the frame behind the side cover. It is pretty large. Not necessarily apples to apples but I redid my 73 500 at the same time, and though I am having charging issues currently, everything else seems to work great, and the are very similar.

You need to be sure that ground is to bare metal and not painted metal. That was my only concern.

[cshanek]

ah, I understand. I will check but the frame was not powder coated.

Attached are some pics from tonight, the buzzer connector, the mysterious brown/red female from loom, and the winker.

[cshanek]

Just tested the ground and it's good. Ran clips from battery to frame also.

[TwoTired]

Br/R is headlight power, fuse to bar switch

Winker connections should be black and grey.

[cshanek]

I have black, white, and green for some reason.  I have been using (or attempting to use black and white)

[Gene]

I have black, white, and green for some reason.  I have been using (or attempting to use black and white)

Black and white is to the coils

[cshanek]

Interesting, the harness connection for the winker has black, white, and green, which I think (just by memory) is the only three connectors of those kind.

[TwoTired]

The only white wire on the wire diagram is for the headlight connection, in the headlight bucket for low beam running to/from the Hi Lo switch on the bars.

Where is your white wire located?  Is it dirty white?  I.E. grey?

The green is used when three terminal flashers are installed.

Black with white stripe is for the coils.

[cshanek]

I have a white wire, along with blue and green (I think all from memory) to the headlamp. It is possible the non-OEM harness I bought, again from VintageCB750 is just colored weird. In fact I think if you look at the white, it has little, hard-to-see red lines at points on it.

[TwoTired]

Wait, there is another white wire from the regulator to the field coil.

Honda's wire diagram clearly shows grey to the winker relay.

[cshanek]

Attached is a pic of the three winker wires I have (winker only has two flat male connections, and I think B and G markings).








Here is a picture, albeit a small one, of the harness I bought . Part #: 24-4004 here: http://www.vintagecb750.com/products/82/monthly-sales. If you look real closely you can see the white, black and green winker connectors stacked on one another.

[cshanek]

TwoTired, Gene, and the picture of the harness I had made me realize the white/black/green connectors are actually run to the harness and the grey and black connector run to the winker. Even the friggin colors match up so this one is on me. That seemed to fix the blinker issues I was having.

Now I have no headlamp, no taillight (unless brakes are applied) and the starter button doesn't work. I have a male black/red, a female brown red, and a brown blue from the buzzer that are all without pairs.

[TwoTired]

Now I have no headlamp, no taillight (unless brakes are applied) and the starter button doesn't work. I have a male black/red, a female brown red, and a brown blue from the buzzer that are all without pairs.

The black/red is another bar control circuit (right side) taking power from the starter button, which powers either the headlight or the starter solenoid from the black wire.  Black/ red is internal harness joined to the Br/red, providing power to the Headlight fuse.
Brown/blue would go to turn buzzer, if you have one, or left unconnected if you don't.  Female connectors can be left dangling.
Brown/red is headlight power which routes from Fuse block to bar control Hi/Lo switch.  Which of those is nearer to the wire you have loose?  I suspect since it's female, it should go to the bar control harness.

Methodology:
Wires unplugged and hot would have a female connector, to avoid making a grounding contact if it vibrates apart.  So, what you have is likely sourced from the fuse block, to be connected to the headlight Hi/Lo switch.

Tail light is the BR circuit, routes from Key switch to tail.  You have the Brown plugged into the harness?

Cheers,

[magnum56]

Give this interactive wiring diagram a peek.  Allows you to enable or disable various aspects of the entire bikes wiring diagram allowing you to easily focus on the components you are concerned with at the moment.

http://oldmanhonda.com/MC/wiring.html

There is an incredible amount of knowledge floating around here, so be patient.
I'm sure these guys can help get you sorted out.   

[cshanek]

Now I have no headlamp, no taillight (unless brakes are applied) and the starter button doesn't work. I have a male black/red, a female brown red, and a brown blue from the buzzer that are all without pairs.

The black/red is another bar control circuit (right side) taking power from the starter button, which powers either the headlight or the starter solenoid from the black wire.  Black/ red is internal harness joined to the Br/red, providing power to the Headlight fuse.
Brown/blue would go to turn buzzer, if you have one, or left unconnected if you don't.  Female connectors can be left dangling.
Brown/red is headlight power which routes from Fuse block to bar control Hi/Lo switch.  Which of those is nearer to the wire you have loose?  I suspect since it's female, it should go to the bar control harness.

Methodology:
Wires unplugged and hot would have a female connector, to avoid making a grounding contact if it vibrates apart.  So, what you have is likely sourced from the fuse block, to be connected to the headlight Hi/Lo switch.

Tail light is the BR circuit, routes from Key switch to tail.  You have the Brown plugged into the harness?

Cheers,

I am on travel for work this week (as of today) so I will have to play some more when I get back this weekend. I did connect the brown/red and black/red connectors and I do not remember it making a difference on anything. Of course other things can be shorted/out of whack.

As always, I greatly appreciate the advice and patience of those that are offerring their assistance.

[Gene]

You'll get there. So close.

[my name is nobody]

http://www.vintagecb750.com/parts/instructions/12-0301.pdf


Do you have this switch, and have you wired it like this? I must admit I've not read this whole thread, so disregard this post if it doesn't apply

[cshanek]

http://www.vintagecb750.com/parts/instructions/12-0301.pdf

Do you have this switch, and have you wired it like this? I must admit I've not read this whole thread, so disregard this post if it doesn't apply

I do have that switch, and the wires, other than the two cases I mentioned earlier, all have counterparts on the loom/harness. I will try to unwire the on/off slider since it says it is optional.

[cshanek]

Give this interactive wiring diagram a peek.  Allows you to enable or disable various aspects of the entire bikes wiring diagram allowing you to easily focus on the components you are concerned with at the moment.

http://oldmanhonda.com/MC/wiring.html

There is an incredible amount of knowledge floating around here, so be patient.
I'm sure these guys can help get you sorted out.   

This is friggin awesome. Just took a look during lunch at work. I will have to play with this a little more this weekend.

[Sigop]

Cshanek,
Did you solve this? I am having similar issues.
Thanks.

[rocket johnny]

have you checked the silicon diode ?    that solved my 76 k6 problems ,,   just a thought

[Sigop]

Thanks rocket; I'm going to open a new thread.

[cshanek]

Is that the rectifier?