Topic: Am I going to catch fire? Electrical advice needed

[enwri]

I know enough to be dangerous, can someone check, if you can follow my explanation, what I've done? thanks.
1977 CB 750 K7
I've attached a 1977 k7 circuit diagram pdf from here, It's not the Australian version as I have parking lights switched from either the ignition key switch, or from the right hand 3 position light switch.
 - off - parklight - Headlight on.

What I've done, and need to ask about is, on the diagram, I've taken the main feed from the + solenoid post, through a 30 amp fuse and heavy gauge cable,, taken it all the way to the headlight shell where I have an ammeter mounted, all the way back to what used to be connected to the + solenoid post. That seems to work well, showing charge going out or in to the battery, discharge at idle, charge just above, changes with lights and flasher loads.

The second change that I'm not sure about is to have fitted a 20 amp relay in the headlight shell, using the original ignition power out from the key switch to energise the relay, fed from the ammeter and it's heavy cable straight to the other side of what used to be the power out from the switch.(power into the loom,) From  Ba on the Ignition switch diagram to IGN on the diagram,  IGN, now triggers the relay, grounded to an empty bullet hole in the parklight ground in the headlight shell..

What I'm not sure about is there seems to be more than one power out from the IGN switch, are the PA, TL1 and TL2 terminals going to cause any weird backfeed issues or have I done anything someone can see that has affected the charging system in any way? everything seems to work properly, charge voltage has dropped from a little high 14.5-15v down to about 13.5-14.0ish.

Will the relay be carrying the headlight current as well as the ignition or do I need to jam more relays for high and low in there as well.

There wasn't really a problem before I fitted a new ignition switch/steering lock from a different model, mine had the plug out in the open under the lock, the new one has cables that I've tucked into the headlight shell as well, tamperproofing it a bit more, Charge voltage jumped a bit after the new switch install.

[enwri]

 Thanks Cal   
The 30 is too much? it only has to be the same as the original 15amp doesn't it. or am I feeding the circuits for the headlight 7amp, tail 5amp, and original main 15amp through it as well. this is where my head turns inside out, I think until I put the relay in the ignition, all power to and from the battery was going through the ammeter, back into the loom at the original place, it had to be more than the total load it would ever get, all circuits combined. So I've used a big cable. Big fuse.
 I was still relying on the original fuses to manage each individual circuit total.

Now I see i'm  feeding into the main circuit after the ign switch with a 30 amp supply, too much.
 I now think I need a 15 amp fuse between the 30amp feed I'm taking from the ammeter circuit, and the input to the ignition circuit back into the loom. fuse in the headlight bucket, not ideal.
The ground I mentioned is just the ground for switching the relay, between the old main feed into the loom after the switch, and an existing ground in the headlight shell. those ears haven't been attached to anything for a long time now, does that mean that everything meant to ground out with the controls is grounding through the headstock bearings? I'm going to earth the handlebars/forks to the loom tomorow..

[Bodi]

Neither the alternator output nor the bike's electrical load should ever be 30A... the "main" fuse is 15A so either a 15 or 20 would be good. Putting a fuse in is an excellent move, running unfused wires from the battery is asking for big trouble - Honda adds an extra sleeve insulator to the wire going to the fusebox.
Using a shunt ammeter is much safer than running thick wires to the steering head but finding a shunt and usable (small and not too delicate) meter is not so easy. After haunting electronic salvage shops for quite a while I found what I needed though. I used a 50mV 20A shunt (four 0.01 Ohm 5W resistors in parallel) and a 100mV meter, set the needle in centre, and made a scale from -20A to +20A.
I'm not exactly sure what you've rewired... but if you bypassed the main fuse by feeding the black wire (from the ignition switch) via relay from your ammeter feed... then 30A would be enough to melt the harness wires if something goes wrong. It's fairly common to add a relay that powers the regulator from the battery "+" via a ~10A fuse, eliminating harness voltage drop from its reference voltage.
I don't understand what you're trying to accomplish by bypassing the MAIN fuse, if that's what you did. That bypasses a short length of wire and the 15A main fuse- but these don't cause a significant voltage drop (if in good condition).
The ignition switch has a few circuits. The PA and TL terminals work the parking light. When the key is ON, the tail light (and a front parking light if you have one) are powered from the TAIL fuse. In PARK these are powered directly from the MAIN fuse. That's because the TAIL fuse power is from the black wire, turned off except with key ON. So to power just the tail light for a parking light, the switch's input power from the MAIN fuse is switched to the tail light. I'm not sure why there are two TL terminals as they are connected together in the wiring, it's likely just because of the switch contact configuration.
You should have a connection to the headlight shell from a green harness wire. Power flow through bearings is to be avoided.

[enwri]

I've been very careful to not have any unfused cable running anywhere,  I was only wanting to take the current off the ignition switch, and have an ammeter in the headlight bucket,   I've had to repair the old melted switch a few times over the years, finally replaced it because the 40 year old key and lock was so worn any key shaped thing could unlock it. The main fuse is still there, replaced the whole block with blade fuses years ago, it's just that now I'm not sure what it feeds other than the relay bypassing the ignition switch. That's what I can't work out. Do the TL1 and TL2 just get bridged in the switch when the ignition is on?  or are they fed from the main fuse circuit. I seem to go dyslexic when trying to follow those diagrams. I'm pretty sure the 15a fuse in the headlight bucket between the heavy 30a fused cable, capable of carrying the total current of everything combined, and the relay power feed into the loom to what used to be fed from the ignition switch, should keep it protected.
The 30a fuse will just cover the big cable from the battery (plenty more than 30a waiting to melt things) being pinched or shorted to ground. It feeds back into the loom where the alternator and main feed used to attach to the solenoid pos.post. Back to the standard power supply point, using all the standard fuses .
It's becoming clearer the more I think about it, I'll read your bit about the PA, TL1 and TL2 a few more times.,it'll sink in sooner or later , thanks.

[enwri]

I've just realized that I should have taken the power to supply the power back into the loom via the relay, from the power into the ignition switch, the original 15a main fused supply. No need for an extra fuse in the headlight bucket. I'll just leave the ammeter circuit alone,  not use it to feed anything.
DOH!!
Just like I would have bypassed the ignition if I hadn't had a big convenient supply right in front of me.
Takes me a while sometimes. .

[Bodi]

The parking light circuit is pretty weird. Some UK model wiring diagrams have an error in the ignition switch diagram to make it more so.

I don't think I had it right before.
Ignition switch wires:
BAT is the red wire, +12V from the MAIN fuse.
IG is the black +12V wire, it feeds the ignition etc and the HEAD fuse.
TL1 is the tail light (and front "position" light if you have one) - brown wire
PA is the "parking light" power - this is spliced with the TL1 terminal brown wire
TL2 is +12 power from the TAIL fuse. Brown/white wire.

keyswitch contact connections:
In OFF, no connections.
In ON, BAT to IG and  TL1 to TL2 (the weird UK model diagrams show all four connected together - wrong!)
in PARK, BAT to PA

So ON powers the tail light from the TAIL fuse as expected. in PARK, the tail light powers from the MAIN fuse, the light will go on with the TAIL fuse removed.

[enwri]

When you asked why I bypassed the original main fused supply I asked myself the same thing  and realized that I only did it because the ammeter circuit was just sitting there in front of my face. I'll be taking that off tomorrow and doing it properly. Thanks for that, that also means the PA and TLs will be fed from the standard supply negating my need to comprehend that diagram, and removing any fears I've had about overating any circuits. I'm still going to try to get it into my head what's going on with the double switched park/tail lights, so thanks for that explanation as well. .
This may take a while. .