Wiring loom

[bruxby-clive]

Whilst I appreciate that I haven't posted much on the forum to date, having decided to take a year out from work after working right through Covid, I had hoped I would have more time to concentrate on pursuing hobbies I enjoy, namely motorbikes and radio control model helicopters & aeroplanes. I turned 60 last December and after discussions with the wife I decided to take at least a year out from the 31st March this year and hopefully not return to work at all, but we shall have to see happens. Unfortunately whilst being taken out for a meal by my boss, on my last day at work, my wife phoned to say that her brother had been found dead by the Police, after they had broken in to his flat after one of his neighbours had reported his concern to them, this ended up with the coroner as a sudden death and my first month was spent sorting everything out and tidying up the loose ends, still a couple to finalise.

After the funeral I wanted to start on a 1980 Z650F1 which I bought from D&K a couple of years ago, after a good clean out of the carbs it ran really well, so I carried out an oil and filter change along with a new air filter and began checking over the electrics and discovered that it was not charging, I noticed that the connections to the reg / rec where corroded and rather that clean them up I just replaced them with new bullet connectors, it was at this point I discovered that the wiring was badly corroded internally, although most of the bullet connectors where in good condition. The picture below illustrates the condition of the wire under the protective outer sheath.

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I then took some voltage readings, firstly ignition switched off, across the battery,

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Then on a brown lead which is feed from the  ignition switch when turned on,

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This showed that in less than 2 meters of wiring that I had a 2 volt drop in voltage due to the corrosion in the wire, and a good candidate for a melted loom at the least and possibly a bike on fire at the worst, a new loom was probably the best option. After placing and order with Vehicle Wiring Products for what I needed I stripped the loom from the bike and made a start on creating a new loom.

I am not claiming that I am any kind of expert at this, I just thought I would share how I go about it and this may help someone else have a go. The first thing you need to do is create a jig to hold the loom so that  you can fit the old loom and hold it in place whilst you  create the new one.

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The screws are fitted at every point that a wire comes out of the loom or there is a significant change in direction.

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This shows the old loom on the jig.

[McCabe-Thiele (Ted)]

Interesting post, I had no idea how looms were made until a couple of months ago - I think it was a Wheeler Dealers episode  where you watched  how the wiring looms were built for vehicles out of production - just like your post but with bigger boards & pegs.

It was a woman iirc who from a sheet of paper put the pegs into the giant peg board for that particular model of vehicle. Sourcing the right colour wiring with trace colours at the right spec might not be easy but very satisfying to build your own new loom.

[BigAl (Alan)]

Interesting project, completed my first F1 loom a number of years ago. Note Yellow/red insulated cable (starter relay) is connected to Black/yellow insulated cable within the main loom. No idea why? but the B1.B2/C2.D1 looms are all wired this way....Good luck with your project

[bruxby-clive]

Hi Ted, thanks for your comments, you can get all of the correct colour wires from either Vehicle wiring products in Ilkeston, vehiclewiringproducts.co.uk or Kojacat in Greenock, kojaycat.co.uk they can also supply the correct size Japanese bullet connectors generally 3.9mm but some are slightly smaller, 3.5mm I think, the smaller ones are only available from Kojacat, as well as all of the 2.8mm and 6.3mm multi plug connectors.

Below are pictures of the cables and plugs ETC that I received from Vehicle Wiring Products, next day service.

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With the original loom secure I start by laying in the wires which travel from the back to the front of the loom by loosely installing cable ties as guides for the cables to travel through, then adding the branches which come off these cables, these being cable tied  tightly to the main cable in the approximate position within the loom. I have attached a number of photos below to show the process but unfortunately I did not take any early on in the laying out of the wires so it does look a tad confusing at first be please bear with me and I will try to explain it through.

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This is the complete loom with the majority of the wires laid in and also beginning to be grouped as to where they are going to end up, note that all of them are over length as it is easy to shorten but a bind to extend.

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This shows the front of the loom I have started to group them into their purpose, IE the 9 pin instrument cluster, the 6 pin and one bullet connector for the ignition switch ETC.

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This shows the rear of the loom, and once again I have grouped the cables by where they need to end up. You need lots of small cable ties at this point.

[bruxby-clive]

Hi Alan, thanks for you comments, and I had noticed that and a number of other odd connections within the loom, such as the brown power supply to the indicator relay being joined to the orange with green trace within the loom and the red with a blue trace which becomes a blue the other side of the instrument cluster 9 pin connector, spent a while double and triple checking that out before sealing it up.

Continuing on from the last post the picture below shows the middle part of the loom where the connections are made to the two switch clusters and the coils.

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You will notice at the top of the old loom there is a blue bullet connection which on the European  model is for the addition of a resistor to be fitted in to the feed to the head lamp high / Low beam switch, I cannot see any point for this to be fitted and have not incorporated this within my loom. Neck stuck out, somebody must surely be able to prove me wrong  . There are a number of other modifications I have also made to my loom by cross-referring to the wiring diagram for the European model, these are I have removed the feeds to the running lights in the front indicators, the 2 pin plug for the indicator sounder and I have reinstated the supply for the side / parking light within the head light and the supply for the headlight flash on the left switchgear which is missing on the American loom.

I still am at this stage missing a couple of cable colours so the loom is not 100% complete but it is time to start joining the branches to the main part, you can buy the brass crimps that were originally installed and then taped over but I prefer to strip, solder and then heat shrink the joints. How I do this is shown below.

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Firstly with a sharp modelling knife I cut to circles about 15mm apart and remove the top of the protective covering to expose the copper beneath.

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Then remove the remainder of the protective sheath.

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Strip the end of the cable you are going to splice in approximately 20mm and wrap around the first cable.

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Now solder the 2 together


 

[bruxby-clive]

Continuing on from the previous post, once you have soldered the cables together you need to protect the joint with heat shrink.

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You need to do this with all of the joints that you do and also there are areas with quite a number of them close together, I try to space them out so not make one part of the loom fatter than the rest and also stiffer as the soldered joint do not really want to bend to much.

Once you have completed all of the joints and installed all of your cables and checked this at least twice, it is time to start tidying up the cables, I start at the back and commence tightly cable tying it all together whilst still leaving the cables over length, but also finally group a cables together that go to specific connectors.

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Back end of the loom

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Middle of the loom

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Front of the loom

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The whole loom laying next to the old one to show the layout. 

[BigAl (Alan)]

It's looking good Clive. The 2 blue wires (normally plugged together) are for the optional Euro models resistor (0.5 ohm/20 watt rating) The OE head light had a 40 watt high & 40 watt low main beams The resistor was inserted to differentiate between the high/low beam brightness for MOT reasons back in the day.

[bruxby-clive]

Thanks for the info Alan, good to be able to understand what it was for.

[Lobo]

Very nice Clive - glad to see the internals soldered. Just this week I’ll be re-sheathing a CB750 loom, but using self amalgamating tape (as suggested by another forum member) in the hope of an easier end to it all.

Just one observation though - and that is your 20mm soldered joints. Is 20mm not a tad too long given the twists and turns around frame components? Is there any real reason why a joint can’t be <5mm, ie opening up the wire conventionally with a simple cable stripper and then binding the new connection around it once before soldering?

[bruxby-clive]

Hi Lobo, no specific reason why I chose an opening of 15mm in the cable to wrap approx. 20mm of cable twisted around the original, other than the soldering iron I use is 75 watt to heat the cable quickly and it has a quite large tip which can melt the outer insulation if it gets to close to it, placing the tip of it in the middle of the joint allows the cable to heat up enough to solder without melting the outer. I try to keep the joints to the behind the headstock so it does not have to endure to much movement. I also use self amalgamating, to wrap the complete loom once completed.

Just a couple of thoughts about cable size to mention at this point, I used modern thin wall cable to replicate my loom. For the majority of the wiring I use 1mm but for the main power cable to the switch (white) the supply from the Alternator to the 20 amp main fuse (White with a red trace), the battery connection (red) and the earth (black with yellow trace), I use 2mm cable. 1mm cable has a capacity of 16.5 amps and 2mm cable a capacity of 25 amps. The reason for the larger earth cable `is to ensure a good earth throughout the bike, some of the branches coming of aree 1mm but the main lead front to back and joining the battery are all 2mm.

[bruxby-clive]

Here we go next instalment.

The first thing we need to do is wrap the loom in self amalgamating tape, starting at the front we keep wrapping it over itself,

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until we have the whole loom covered,

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Then we need to to install the additional PVC sheathing to protect the loom as it goes round the head stock.

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and then secure it with a little more self amalgamating tape.

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The next thing to do is fit all of the connectors.

[bruxby-clive]

I started in the middle and fitted the 4 & 6 pin multi connectors and single bullet connectors, these are all just crimped on , I apologise in advance for the quality of some of the photographs.

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This shows the 4 pin connector to the right handlebar  and the bullet connectors for the headlamp from the left handle bar,

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Both handle bar switch connectors completed with the additional required bullet connectors.

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The four cables for the two 10 amp main fuses

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The above installed in their multi pin connector

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Finally the front of the loom, with the 6 pin ignition switch and 9 pin instrument connectors along with front brake light switch, indicator and earth bullet connectors.

[bruxby-clive]

Finally for today a couple of pictures of the completed loom.

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[Lobo]

…very nice.

I assume you wrap the branches < the main loom? How do you secure the ‘last turn’? Is the self amalgamation enough?

Was recently trying to find a wide SA tape to replicate the original (eg 30mm) - no success. I note you’re using a 15mm or so tape.

Not worked with thin wall before; do the smaller diameters give issues with crimping? If so tips as to best succeed; which tool are you using?

I’ve a 50yo car I want to reloom - would you suggest thin wall over conventional - my main concern is (as mentioned) the terminations let alone the ‘unfriendliness’ of a thin-wall under dash spaghetti. Weight, nor space are an issue…

Ta,
Simon

[bruxby-clive]

Hi Simon

To answer your questions;

1. I find wrapping the self amalgamating tape around itself before moving down the branch is enough, although I go around both sides of the branch before moving on.

2. With the 1mm thin wall I have doubled the stripped end over on itself before crimping to provide a bigger area for the crimp to bite on. I use this crimping tool  https://www.vehiclewiringproducts.co.uk/c-51-crimp-tools/c-119-non-insulated-terminal-crimping-tools not the greatest but adequate if only doing the odd loom, if I was doing it regularly I would go for a ratchet crimper like this;  https://www.vehiclewiringproducts.co.uk/c-51-crimp-tools/c-119-non-insulated-terminal-crimping-tools/p-269-ratchet-crimping-tool

3. Given that thin wall has a greater current carrying ability and makes the loom thinner in size, I would always use it, you can still get the old style cable, but I think the range of available colours may not be quite so good. It is probably down to your individual choice, although hopefully, Big Al may be able to provide a more technical view on the matter, he is far more knowledgeable than myself.