Here are copies of the colorised wiring diagrams I created, based on the original Honda black and white diagram for the UK-market 1978-82 C90. Earlier diagrams are available below.

If you aren't familiar with reading this type of diagram (it is not has hard as it first appears!) then you can read more about them here:

Honda C90 - electrical system overview
Electricity Learning the basics of automotive electrical systems, even the simple system used in the Honda super cub, was something I approached with a little trepidation. My schoolboy science got me as far as grasping that the electrons in conductive materials like metal can “jump” between atoms, displacing others in
The Small WorkshopNick

Complete wiring diagram (1978-82)

complete Honda C90Z (1978-82) diagram

Subsystem diagrams

The diagram can be broken down into separate 'subsystems' to make them easier to understand. These are shown below:

electrical Subsystems (Ignition, Charging and Lighting)

Earlier 6v models (1967-77)

The C90s in the decade before the C90Z was introduced had a side panel mounted ignition switch and a light switch mounted in the headset.

the other main changes made when the C90Z was introduced was the introduction of a parking light and a turn signal indicator bulb in the headset.

There were at least two revisions to the wiring, the most obvious difference being the change from a two wire ignition switch to a 4 wire version.

1967 wiring diagram

1973 wiring diagram