1982 CB750F...Better Devil

[Maritime]

Yep. I ruled out anything before your fuse panel as it.powers all the other things that do work. Your test light should light on both sides. The in and out of the fuse. If just the out works your good bur if you're not sure which side is which, check both. I feel like you will find the issue at your starter button. Ive had 3 bikes and 3 with headlight issues and all were corrosion in that spot. Good news is you can dismantle and clean it.

 

[Maritime]

Honda puts the power for headlight through there as when you push the button, it turns off light and activates the starter so less drain on battery during the start. Then whwn you release it turns light back on. The slide switch gets green and stops conducting from lack of use.

 

[Jimbonaut]

Ok Mike, here’s what I got (apart from shingles...)

- fuses all good

At starter button -

- blk/red good
- blue/wht good

At high/low switch (switch in low) -

- white no power
(blue also no power)

At high/low switch (switch in high) -

- blue no power
(white also no power)

I also checked the blue/white wire at the high/low switch - power with switch at both high and low.

I did rebuild all the switches which is also probably relevant info, but was pretty careful not to mess anything up or damage any of the wiring. Think I may have spannered something in one of the switches?


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[Jimbonaut]

Judging by what you said I should have power at the white or blue wire at the high/low switch (depending on the switch position) but I don’t.


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[irk miller]

The Blue/White wire is what feeds power from your starter switch to the headlight. It is fed by the brown/black wire from the fuse box. Have you checked power at the starter switch on the brown/black wire and the blue/white wire with the ignition switch in the on position? You want to check for power, and continuity. When the switch is released, you should get continuity between the blue/white wire and the brown/black wire at the switch. If you have both, then your issue is further down the line. The dimmer switch switches between white and blue. Check power AND continuity between the blue/white wire and the blue wire; blue/white wire and the white wire. Check for continuity between your green wire AT THE LIGHT plug and frame ground. Your lights share a common ground with your horn switch and your clutch switch. If you changed some of the wiring, you may have inadvertently eliminated your headlight ground.

 

[Maritime]

What Irk said. Does the blue white wire leaving the starter button going to the headlight have power? If yes then your headlight switch has an issue. If no your starter switch has issues.

Edit i see the blue white has. Power from your post. So something is broken/miss wires in your headlight switch. Open it up and look

 

[Jimbonaut]

Guys, as always I really appreciate your help with this. I took both switches completely apart a few weeks ago and rebuilt them as they were in a sorry-ass state - full of spider's nests and the usual 35 year old crud. Cleaned them all up and reassembled, dielectric grease on the contacts. As far as I could tell there was no damage to any of the wiring, and everything went back where it should.

I did just take the starter switch apart just now. Here's the scoop on that. This photo is with the starter button itself removed, and also the two tiny little contacts. I checked each wire for power -

- and that's what I got. So, different results to when the starter button was installed and the switch itself all in one piece. Then, blk/red had power, and blue/white had power. With the starter button (and its contacts) removed blk/red had power but blue/white did not. Could that be something to do with the problem? Could it have something to do with these little contacts being installed incorrectly -

?

I have no idea how universal these starter switch internal assemblies are, so if you're not familiar with the set-up those two little contacts sit on top a tiny spring in a tiny recess on the starter button shaft -

Is it possible that I'm missing a piece? Could the problem be down to those two contacts touching each other? Do they need to be not touching? Because the surface area of the top of the spring is so small it's very difficult to separate those two contacts without them falling off.

So the blue/white wire feeds power from the starter button to the headlight. I'll need to reassemble the starter switch (correctly - if I got it wrong before) and check. I'll go through all your instructions and try not to have a stroke. That'll be tomorrow - in the meantime what do you think about the starter button? Look ok?

 

[irk miller]

Just to go over how to read your drawings, which also will give you an idea how things work. In your drawings, the barbell shapes are your contacts in the position designated in the drawing.

When you push the starter button, yellow/red contacts black/red. Lights go out because the contact moves away from the blue/white and brown/black contact. Those brass pieces in your hand are those barbells in the drawing. If you installed it in reverse, or wired it in reverse, then your lights should go on when you hit the starter button. If a spring is missing, so the contacts don't actually make contact, then you will have an issue.

Park- contacts between brown and red. Brown is your tail lights. On- contacts between brown, brown/white (all lights) and black and red (coils, ignition, battery power, etc)

Low, just white. High, just blue. N-both blue and white.

You do not need to be checking for power on circuits to find fault. In fact, IMO the best way to test switches is with continuity. If you hook your meter to the yellow/red and black wire to your starter switch and push, it should beep. When you hook it to the blue/white and brown/black wires, it should beep when you're aren't pushing the switch.

In other words, if you hook a meter to each side of the barbell in the drawing and set the switch to the position in the left box of the drawing, the meter should beep.

 

[Jimbonaut]

I’m going to reread your reply a few times Irk and really get my head around it. Thanks for taking the time to go into detail here and for showing me the ropes. Before I get to the garage tomorrow one quick question - the meter. You mean multimeter right? I’m not sure mine beeps but I really don’t know much about how to use it. Can you tell me what I should turn the dial on the thing to point at? I’m also not sure which end to put where (black end or red)?

So far all I’ve been using is the test light thingy.


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[irk miller]

Yes, your multimeter. Usually there is a setting under the ohm function for continuity. It's often designated by the speaker/sound symbol.

The symbols on that multimeter where the dial is set, clockwise from top is ohms, sound (continuity), capacitor, diode. When checking for continuity the screen will read OL.

 

[Jimbonaut]

Ah, I understand now. I had no idea about continuity in terms of electricity before you talked about it, and even less about how to check for it. Cool cool, definitely learnt something here. That’ll be the first thing I do in the morning, cheers man



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[pidjones]

Touch the two meter leads together on ohms scale to see if you have the sound function gor continuity. Mine has it, but my ears can't hear the high pitch. On the meter face it will read a low value with them touching (should be zero, but the leads usually have a couple tenths resistance and the electronics in the meter may be a bit off.)

 

[Maritime]

Jim, sometimes those 2 little contacts on the button are bent and they don't make contact well. when the button is out they contact the 2 pads that make power go from the black brown to the blue white like Irk said. when all assembled and your key is on does your test light come on when touching the blue white wire? if so there is nothing wrong. You can also push the starter button and see if the light comes on touching the red yellow, or if you have it hooked up the starter should turn. If you have power there correctly you need to move to the next switch and check the ins and outs. the hi/low. if you test the blue white going into that switch and there is power, something is off in the headlight switch. If you don't have power there is a short in the blue white wire. If there is power and you check the white out for low beam and there is power there is a short in the wire to the headlight plug. If no power there is a problem with the contacts inside the switch.

 

[Maritime]

Check these. Yellow lines point to the contacts, file a little to remove corrosion or glazing. not too much or you'll need to solder them. Green lines, make sure these are not bent they need to be flat or even arched away from the spring a little, not dipped. also you can stretch the spring a bit to help force against the pads in the switch. Also your spring needs to be clean and corrosian free as well as it connects the 2 clips with the nipples.

 

[Jimbonaut]

Thanks again for all the insight and help gents. It's as invaluable as always.

Okayyyy, deep breath.

Firstly, now knowing what continuity means (and more or less how to check for it) was a great lesson. On my multimeter I'm pretty sure it's here -

It doesn't beep but I'm half deaf anyway from two decades spent inside bass bins so screw it. It just reads 00.0 if there is continuity. Armed with new skills, here's what I checked -

"If you hook your meter to the yellow/red and black wire to your starter switch and push, it should beep." - meter reads 00.0 = continuity
"When you hook it to the blue/white and brown/black wires, it should beep when you're aren't pushing the switch." - meter reads 00.0 = continuity
"when all assembled and your key is on does your test light come on when touching the blue white wire? if so there is nothing wrong." - test light does come on
"You can also push the starter button and see if the light comes on touching the red yellow" - test light does come on

So far so good. Moving on to the hi/low beam switch -

"If you have power there correctly you need to move to the next switch and check the ins and outs. the hi/low. if you test the blue white going into that switch and there is power, something is off in the headlight switch" - test light does comes on
"If there is power and you check the white out for low beam and there is power there is a short in the wire to the headlight plug" - test light does not come on (when you say white out do you mean test the white wire where it is soldered to the headlight switch? That's where I tested it) so...
"If no power there is a problem with the contacts inside the switch" - I took that thing apart 5 times and cleaned it to within an inch of its life. Unless it's busted, the wires all look good, as do the contacts.

I checked continuity from the blue wire at the headlight switch to the other end at the headlight plug - good continuity
I checked continuity from the white wire at the headlight switch to the other end at the headlight plug - good continuity
I checked continuity from the green wire at the headlight plug to the other end where it grounds to the coils - good continuity

This is the connector from the starter button switch to the connector on the harness (you can see the blue/white wire) -

And this is the headlight plug - with a test light I get no power in any of the three wires -

Here's the hi/low switch -

and the other part of it -

I also checked to make sure that my new led headlight actually works, hooked it up to a battery charger and it works just fine. I also checked and cleaned the contacts in the started button assembly, making sure they weren't bent and that the spring was clean.

?

 

[irk miller]

Sorry to bring the bad news, my man, but that setting is for diodes and your meter does not beep for continuity. You can, however, check for current/continuity with an ohm function, since you have to have current to have resistance. A break in current = unlimited resistance.

 

[Jimbonaut]

Sorry to bring the bad news, my man, but that setting is for diodes and your meter does not beep for continuity. You can, however, check for current/continuity with an ohm function, since you have to have current to have resistance. A break in current = unlimited resistance.

Fuck me running. Ok, back to the drawing board. Which ohm setting should I set the meter to Irk, there are 5?

 

[irk miller]

Do this for starters. Set the meter a 200 ohms and touch the two leads together. You should get somewhere around 3 ohms. This is where you can set it.

 

[Jimbonaut]

Ok, and what will the meter read if there is continuity?

 

[irk miller]

Also, usually when you put a lead on each side of a switch, then hit the button, your number change or you get reistance numbers at all from OL or whatever your meter reads when there is zero resistance or unlimited resistance.