Re-wiring, Part 4 (Starting to build the main loom) – 28 Nov 2015

If you remember, I laid out the old, manky main loom on the bench and took off the sleeving and insulating tape so that I could draw my wiring diagram. Now I needed to put it on the bike so that I could examine how it was laid out.

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This is what I came up with.

Final wiring loom layout

It’s impossible to see what’s going on in that photo so here’s my pdf document – Final V7Sport wiring loom layout. This can be zoomed in on or printed out as a poster. It’s designed to come out as a 3×3 poster using A4 paper but 3 sheets should come out blank. It’s the only way I could get it to work with my printer.

The first thing was to go back to the old loom and measure for the main sections of sleeving and to mark where groups of cables need holes to exit. The various individual wires could then be threaded through and temporarily held together in bunches with smaller diameter sleeving. This gave me my loom, incorporating my modified wiring, but without any terminals fitted.

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I now needed to offer it up to the bike to be sure all the wires would come out in the right place and would not be too short. For this to work I needed my replacements for the original fuse box and starter relay in place.

This is the fuse box I’ll be using.

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The original fuse box had an internal link. I couldn’t see an easy way of doing this inside the new box.

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So I had to produce an external bridge cable. Note the “piggy-back” terminals at each end.

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Fuse box fitted to inner mudguard. It’s not as pretty as the old one but is going to be more reliable.

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I need a different starter relay and wiring to the original because I’m using a later pre-engaged starter motor.This is the old type relay.

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The replacement 40A relay and its connector were fitted to the original bracket. A screw is also needed in the unused mounting hole in the bracket as the rubber cover is held on by latching over the two fixing nuts.

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The switch loom was fitted so I can establish where its connections on the main loom need to be.

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This loom passes through lower hole in left hand side of the frame gusset.

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I went back to my new main loom on the bench and fitted the terminals to the wires which connect to the fuse box. I could then work forward checking the layout of the rest.

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Having done this, I felt that the pieces of sleeve were restricting the cables and removed them to give more flexibility.

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The rest of the bare loom was fitted to the bike and I checked the length of cables. Thankfully none were too short and all appeared to be in the right place. A few had to be shortened. The main loom is fed up through the other, larger hole in the left side of the frame then up to the warning lights and instrument cluster.

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The speedometer and rev counter have been fitted with earth tags.

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A small link wire was made to join these to the earth return for the “lights on” warning lamp. I’ll include this when main loom is made up.

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More soon!

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Re-wiring, Part 3 (Switch loom) – 24 Nov 2015.

My next job was to produce the other small loom which is soldered to the handlebar lights and horn switch. I’m going to use the original chrome “snuffbox” switch which is in good condition without any melted contacts. The wiring is also in very good condition apart from one point where it looks like it has got trapped and cut the sleeving and the insulation of one of the wires inside. There was also a very perished rubber “T” piece in the loom. I hunted for ages trying to find a replacement and eventually came up with a nearly identical item at Disco Volante Moto here in Wales.

I removed the old sleeving and wiring terminals after checking that the wires were plenty long enough. The damaged insulation to the horn wire was repaired with heat-shrink sleeve.

I had planned out and drawn the alterations to the switch loom.

Switch loom

As I am adding relays to the headlamp circuits, the two wires (green and green/black) which originally went from the switch to the headlamp needed to be extended and diverted back toward the main loom. I don’t really like to solder joints in a loom as they restrict its flexibility. However, here I felt it was the best option because, if I were to unsolder then resolder the contacts at the switch, there’s a good chance of me damaging it.

Two new wires then need to be brought up from the main loom to the headlamp. As these have the same colour code as the originals, I added purple heat-shrink tags to them.

The earth return for the horn circuit was originally via the switch casing to its fixing screws, the switch-fixing screws to the clutch lever bracket, the clutch lever bracket to the handlebar, the handlebar to the fork stanchion, the fork stanchion to the headlamp bracket, the headlamp bracket to the headlamp shell, then the headlamp shell to the headlamp earth wire which is grounded to the rectifier bracket. A jumper wire is then needed as that bracket is mounted to the painted frame with rubber washers! I don’t think this is a reliable way of doing things.

However, improving this earth is difficult as there’s no way to put a soldered connection on the chrome switch casing. The best I could do was to add a wire with a tag to a fixing screw inside the switch.

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A 3.5mm solder tag was nice and snug, requiring the screw to be wound through it but, is at best, optimistic as a long-term solution. I did test continuity between the switch case and the end of the cable with my meter. At the moment it’s very good.

I used “bullet” connectors on the headlamp wires. Plugs on the switch wires to the relays and sockets on the load wires from the relays to headlamp shell.

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Re-wiring, Part 2 (Charging loom) – 23 Nov 2015.

I thought I would start with the easiest loom first. This is the one that links the alternator, rectifier and regulator. I had already decided I would use 2mm² cable for this.

First I dismantled the old loom with its oxidised wires, cracked insulation and dodgy terminals.

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I decided to reuse the body of the three-way connector for the regulator and used a bit of stiff wire to release the terminals. I had bought some “with latches” ready. I also managed to find a replacement for the “long grommet” used where the cables exit the alternator housing. I’ve had this stashed for a while. I think I got it from somewhere in The States.

Copying the old loom was easy but, crimping the connectors was not! I’m still having problems with my damaged wrist and hand. My ratchet tool for uninsulated terminals needs more strength to use than the one for the insulated type and was flippin’ tough going. It was why I had to use those horrible red insulated things when I did some jobs on The Fire Bike a while back. Never mind. I persevered and slowly got the job done then went to soak my hand in cold water!

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I added the extra wire as planned in case I upgrade to the later, more powerful alternator at some point – it’s the grey one wrapped in amalgamating tape at both ends. Replacement rotors for the original low-output alternator don’t seem to be available any more.