CB750 Wiring Issues

[Oddjob]

How the hell have they managed that Roy? the brown wire comes from it's own fuse in the 3 fuse fusebox, surely they'd have copied the original wiring? even if the colours are different they'd need the wires to go to the right place. Where's this new loom come from?

[royhall]

I think the looms are made in Vietnam, I have had them before and they were spot on. An example is the flasher relay, goes into the loom from the flasher as light blue (wrong) and appears again in the headlamp as grey (correct). Works okay though after a bit of multimeter time. When I built my 750F2 I was able to re-use the loom and switchgear and the wiring was simply connect black to black etc. Done in a morning and right first time. I'm thinking this week I will go to the lock-up and bring my other 750 home, take the headlight off and see if I can copy what's in there onto the K5 (the wiring diagrams looks virtually the same).

[Bryanj]

Going back to basics, start with the RH switchgear
1 does it have a lights on/off
2 1,2 or 3 wires to starter button
3  what colour wires go where

Its this bit that buggers up most wiring faults

[royhall]

Thanks Bryan. Not in the garage now until Tuesday, will check and get back to you. Thanks for the help.

[clinto]

Hello,in your start of this topic you post a colour wiring diagrame.Where can this be found?
I am shortly wiring up a K5.
Ta

[royhall]

It's in the back of the Clymer workshop manual.

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[clinto]

Thanks for that.
The clymer manual that I looked at is B/W,is yours a special edition?

[royhall]

Mine is the 8th edition 26th print run. In other words the latest edition last revised in 2010. It says Colour Wiring Diagrams on the front cover. Hope that helps.

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[Oddjob]

Does the high/low switch have a neutral position Roy?

Bugging the hell out of me why they show a neutral position if it doesn't have one, also poor attention to detail that they got the contact information wrong on the high/low diagram, you'd expect better from such a well known producer of these books.

[royhall]

Can't get into the garage until tomorrow afternoon, the doors are blocked with a trailer. Will get back to you tomorrow as it's bugging me as well. Woke up at 3am this morning and the bugger popped into my head, that was it for sleeping.

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[Oddjob]

Just been studying that wiring diagram Roy and the design Honda did is terrible. Yes, the fuse box has 3 fuses, just like the 550F has, however everything runs through the main 15A fuse, if that blows the other 2 fuses are dead. Surely the idea is to isolate certain parts of the wiring so that in the event a fuse blows at least some other parts still work. Imagine your on a dark unlit motorway or even worse a side road with loads of bends, the main fuse blows, suddenly all the lights go out, your still doing 70 and have no idea where the road is going. IIRC on the 550F if the main fuse blows the lights stay on, if the lights blow the engine still works, how is that not a better system? and if so why fit such a bad system to a K5?

TBH it wouldn't be hard to convert it to something like the 550F system, disconnect the inlet wire from the headlight fuse and wire it up to the red wire that's unused from the stater solenoid.  At least you'd still have a headlight working if the main fuse blows.

[royhall]

I couldn't agree more Ken. It's all poorly designed. I mean, who in the world uses black for live feed

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[SeanFD]

I've been puzzling through this with everyone else.
The earlier 750's only had one fuse - 15A; this setup is no different really as all the power comes through fuse to the the key switch  and then to the lighting and other circuits. So if the main fuse goes, there's nothing

Here's a wiring diagram schematic that seems to be the same asa the one Roy posted, but it has the connection in the dimmer switch correct. The colours are also a bit easier to identify.

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I have a question, though; how many positions are there on the indicator switch? What are the L1/L2 and R1/R2 about? L2 and R2 give you the buzzer and L1 and R1 don't. Is it held on position 1, for a short flash, and locked in position 2 for a longer flash?

I had a similar problem when I changed the handlebar switches on my K2 for later ones. I started with the switches and worked out what each individual switch position would do - e.g. turn on one indicator at switch and see which 2 wires were connected - grey + orange or light blue. Once you know this you can connect the switch wires to the loom wires to do what you want them to do.

Now the white wire from my RH switch (Low beam) turns on the pilot light; the dark blue wire (high beam) goes across to the LH switch to the Hi/Lo/PA switch.

I used a whiteboard and coloured markers as I went along to record everything. Took ages! After it all I drew a schematic using Powerpoint. I won't attach it here to avoid confusing people, but happy to share it by PM if anyone wants to see it.

[Oddjob]

AFAIK Sean the R/H switch on the USA K5 just does on/off, nothing else. All it does is turn on the lights which in turn feeds the fuse that controls the main lights, this only has Hi/Lo so no neutral position. The L1 and R1 are when you hold the switch across with your thumb, for when you don't want the indicators to stay on, like passing a car or as you say a short flash. The L2 and R2 are when the buzzer sounds which is why the buzzer operates as it's to remind you to switch them off.

[SeanFD]

If I understand that wiring diagram correctly, the headlight on/off switch is redundant; power to the hi/low switch comes in there on a Br/R wire from the general Br/W lighting wire. The On/Off switch connects the lighting circuit to the black power circuit, but the former is already connected at the ignition switch.

According to "Honda 750Expert" the switch was removed for US K6 models. An extract (he shoe thing is 130+ MB) from his book/manual is attached. You can get it complete here:

honda750expert.com