Electrical System
This is the schematic glued to the back of the headlight:
This is a schematic originally published by Ducati, titled: "ELECTRICAL EQUIPMENT with static regulator of current"
There is an omission in the above schematic. On item 16, the terminal block in the headlight, you'll notice one of the eight terminals (the one adjacent to "SP") is empty. That should show a black wire with a white mark that leads to the coil where it is terminated with a ring-tongue terminal and grounded at the coil's clamp. It's probably a redundant connection, but it's in the wiring harness never the less.
My main wiring harness didn't look bad where the wires were protected by the headlamp shell. Note the little gold-colored 'bullet' connectors that mate with both the terminal block in the headlamp bucket and the terminal block on the regulator under the seat. Those bullet connectors measure 4mm in diameter at their widest part.
The back end of my wiring harness reminded me of the way my brother and I ran speaker and power wires to his under-the-dash 8-track tape deck in the early 60s. The back end of this harness had splices of wire bits that were often spliced a second time - inches from the first splice, and often times changing colors or gauge as it passed under a wad of electrical tape.
A new wiring harness was made using 14 gauge stranded THHN wire. This is commonly called "building wire". Its PVC insulation resists oil, water, gasoline, acids, and abrasion. It can tolerate a high temperature of 194 degrees Fahrenheit. It is available in a variety of colors, which is handy when you have to run 8 wires. Also referred to as "AWG 14" rather than 14 gauge, the wire can carry 15 amps of current and is equivalent in copper cross-sectional area and physical diameter to the original metric wire size used by Ducati. The Mach 1 has a 60 watt alternator, meaning it can only supply 10 amps (6 volts x 10 amps = 60 watts), and so the 15 amp capacity of 14 gauge provides a nice 50% safety margin.
The original 4mm bullets were substituted with 14 gauge butt splice connectors, which fortunately measure 4 mm in diameter! These butt splices were soldered in place, not crimped as that would deform the shape of the 4mm cylinder.
Coil wires exit the heat shrink tubing at the appropriate place. Incidentally, the black wire in this photo is the wire that's omitted in the electrical schematic.
Old, and new.