Re-wiring, Part 1 (Planning) – 22 Nov 2015.

As I said last time, I like wiring. I know that electrical work frightens a lot of people. Some of whom wouldn’t think twice about undertaking any sort of complicated mechanical job. As a child I liked making circuits with batteries, lights or buzzers and went on to wire model railway layouts, build radios, amplifiers and other small electronic projects. This is not my first total rewire.

I find it all very absorbing and I spend ages working everything out. I’ve held off posting anything here until now as I wanted to make sure that any diagrams would be right.

The first thing I did was to examine the various original wiring looms from the bike. These are;

  • The main loom. This runs from the instruments back to the fuse box under the seat. It possibly went all the way back to the tail light but, if it did, mine has been split.
  • A switch loom soldered to the lights and horn switch.
  • A charging loom linking the alternator, rectifier and regulator.

The last two are easy enough but the main loom is more complicated. Although original, my loom has been wrapped in insulating tape (by me) many years ago. Here is a composite photo of what I had.


I had labelled all the connections before removing it from the bike. Now I cut off all that horrible sticky insulating tape and kept the shape of the loom by holding it together with cable ties. I was expecting to find cracked insulation and dodgy connections and did. However there were some soldered joints and broken wires as well. Not my work.



Having done this, I was able to draw a diagram of the loom and then a schematic wiring diagram after consulting the one in my manual. As usual the colours didn’t quite match up. This is what I came up with. There are no direction indicators.

Original V7Sport wiring diagram

As it’s hard to see what’s going on in that photo, the same wiring diagram is here in pdf file format V7sport original wiring diagram and can be saved and printed as a four-A4-sheet-poster (2×2) if your printer can manage this sort of thing.

I am going to make some changes from the original.

  • Two relays will be used for the headlamp main and dip beams. This prevents the switch contacts from being melted and becoming unreliable. I don’t know if this used to happen with the original bulb but, it’s definitely a problem as soon as you upgrade to an H4 halogen. The modification also reduces the voltage drop at the headlamp giving the best light output.
  • I am going to use a later pre-engaged starter motor as fitted to bikes like the 850T3. These are gentler on the starter ring gear although they must weigh nearly double the original. This means a different wiring layout for the relay.
  • I shall also include an extra wire in the charging circuit between the alternator and rectifier which will remain disconnected. This is so that I can change to the later higher output type if I want. This needs the extra connection.
  • Finally, I’m going to run an earth return wire from the front of the engine block connecting the earth points together and finishing under the seat. This means I should not have to carefully scrape paint from frame fixings to get good earth return connections. It takes very little extra effort.

So this is my new schematic diagram.

Modified V7Sport wiring diagram

Once again this is available as a more readable pdf to download here Modified v7sport wiring diagram.

Wiring will be in 1mm² and 2mm² thin wall cable. The heavier type will be used mainly for the charging and ignition circuits. 1mm² will be ok for the rest.

I have got on with actually producing the new wiring so will be back with part 2 soon.


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