=== Quartet Harness ===
I discovered that I also have the 'Quartet Accessory Wire Harness' (Part No '''Honda 08A30 MCS 100''') Although there's a [https://www.amazon.com/Honda-08A30-MCS-100-Accessory-Wire-Harness/dp/B00656YJ82/ Quartet Accessory Wire Harness] '''Honda 08A30 MCS 100''' Although there's a link on Amazon], it is unavailable for purchase there.
[https://www.st-owners.com/forums/attachments/0007-st1300-quartet-harness-installation-20051207-01-01-pdf.5357/ Quartet Harness Installation instructions] can be found on the ST-Owners forum with a [https://www.st-owners.com/forums/attachments/honda-quartet-harness-power-plug-installation-instructio-pdf.5965/ photocopy of the original 4-page install instructions] too. (Those are linked from [https://www.st-owners.com/forums/threads/st1300-quartet-harness-installation.7714/ this forum post] but without comment, and the whole thread is pretty content-free.)