Pleased I could help.
Initial outlay has been quite a bit more expensive than buying a pre-made harness
Bear in mind that, unless your bike was absolutely bog-standard electrically, you'd still have had the expense of tools, some terminals and wire to modify any pre-made harness. Also, apart from British Wiring in the US (and apparently even them not always), every other harness maker at best copies all the the cheapo compromises 'original Lucas' put in every '71-on harness; some (guess who?) add a few more of their own ...
The nice thing about your bike's harness when you've finished is the only compromises it'll include are the ones you put in.
Plus you'll have the tools and a few spares for the next project ...
I’m in over my depth.
You aren't, trust me.
Might look a bit daunting now but, as long as you continue to work methodically, it'll appear much clearer quickly.
One of the 'moments' I remember from my first rewire was when I'd stripped off all the black tape ... then there was the wiring diagram in Glorious Technicolor.
The other thing I didn't do on that first rewire but I've done on a few subsequent is copy and blow up the wiring diagram to a larger paper size, have the local print shop run off a copy, go over the black lines with coloured pens or felt-tips, pin it on the garage wall by the bike and tick off the wires as you install them. Or, if you're more computer-savvy (or have a bribable teenager), knock up a full-colour copy of the diagram is one of the myriad circuit-drawing computer packages?
I've read about running discreet earthing wires (red) from the indicators but what about the rest of the components which are earthed? For example all of the lamps in the headlight are earthed and if I run a separate wire from each one that's a lot of red wire which has to find it's way back to the battery.
Uh-uh, remember what I pm'd you? One 8-way (4 wires in each end) bullet snap connector inside the headlamp shell, another somewhere under the seat. Then individual component Red wires run only as far as the nearest 8-way. Using your list: Red wires from headlamp, pilot, two indicators, main beam idiot lamp, speedo. 'n' tacho. illumination run as far as that 8-way snap connector inside the headlamp shell; that's seven Red wires, the eighth is the 28/0.30 Red wire that'll connect to engine and the other 8-way under seat; a Red wire from the latter connects (through the main fuse) to the battery +ve terminal.
Is it good practice to try and eliminate the frame as the earth conductor as much as possible, how practicable is this?
Unless your bike has a non-standard harness now, when you strip off the existing tape or cloth, you'll see it already has Red wires to pretty-much every electrical component mounted certainly on cycle parts (bar the indicators). Lucas had by-and-large eschewed "the frame [any cycle parts] as the earth conductor" for many years before your bike was built.
For this reason, I never incorporate any cycle part as any part of an electrical circuit - e.g. a short wire from a component to the nearest part of the frame; it's certainly what the Japanese makers have done for decades ... and ime it's simply never long-term reliable.
Spark plugs and oil pressure switch do use the engine as an earth conductor. While it'd be possible to eliminate even that with a Red wire to each mounting, in practice, I've found one Red wire attached between the harness and somewhere on the engine to be fine for all electrical components on the engine.
I've bought some more fuse-holders to supplement the existing one to the negative battery terminal.
Uh-uh. You need to be absolutely crystal-clear about this because it's important.
Because the electrics are 'positive earth', the main fuse should be in the one-and-only Red
wire attached to battery positive
This protects against the not-unknown possibility of something metal accidentally touching the battery negative
and some other part of the bike. In this event, because the bike's electrics are 'positive earth', any
metal parts of the bike can form a conductor to any wire attached to battery positive. If there isn't a fuse in the one-and-only Red wire attached to battery positive
, this becomes an unfused short-circuit and damage will result very
A fuse attached to
battery negative cannot prevent this short-circuit because the short won't be through it.
The only exception I'll use is the +ve wire from an electronic ignition 'box', which I also connect directly to battery +ve. I don't put a separate fuse in this, on the basis the wire's either fully-insulated from the 'box' or, if it has to be extended, extension and connection are also fully-insulated.
I've read here that it's sensible to fuse other circuits but which ones and where would the fuses go?
I connect the DC wires from the reg./rec. directly to the corresponding battery terminals. Ime and mho, the reg./rec. -ve wire should not
be connected to a break in the Brown/Blue wire (as the original rectifier and Zener were), the reg./rec. +ve wire should not
be connected to the bike's other Red wires, definitely not to another sundry bit of bike.
If you accept that advice, then put a fuse in one of the wires between reg./rec. and battery.
Beyond that, fusing individual circuits is definitely desirable, but vexatious to actually implement ...
The primary problem is most individual circuits diverge inside the headlamp shell - a White wire runs from an ignition switch terminal to supply: ignition (via the handlebar kill switch), oil pressure idiot lamp, brake lamp switches, indicator relay, horn and headlamp flash buttons; Brown/White runs from an ignition switch terminal to supply the Lighting switch, which supplies headlamp, pilot lamp, rear lamp and speedo. 'n' tacho lamps. Eight fuse holders crammed inside the headlamp shell ...?
. fuse an electronic ignition, but near the 'box', usually under the seat;
. because I use relays to switch the headlamp, and relays that take a blade fuse are common, the headlamp ends up fused.
Apart from them, potentially anything
connected in any way to battery negative (on a 'positive earth' bike) might
cause the main fuse (connected to battery positive) to blow and bring the bike to a halt in darkness. As it's my arse on the line, I do the best wiring and connecting I can.