Are you sure that the 2022 and earlier model has that jack? My 2021 has the ignition switch, headlight plug, and turn signal plugs in there. I suspect the USB kit is meant to use the
accessory power port that seems to only be present on the Japanese market bikes. If the part is specific to the Japanese market, Japan has an official language of Japanese, so that may be why there aren't any translations included. You can use the Google Translate app on a smartphone with a camera to get a rough translation.
If you want to tap
switched power the ignition switch is likely your best choice. It's a very simple path to switched power that is easy to read on the wiring diagram, close to the meter stay port, and a (relatively) thick gauge of wire. The red 4-pin service connector (DLC) by the battery is also switched, but might be less convenient if you aren't just plugging a connector right into it.
If the 2023 (JA65) still uses the same 3-prong ignition switch as the earlier model (JA55) and the same wiring colors then you can see here for tapping the ignition switch:
For those of you who have mounted a USB charger into the factory spot by the handlebars: 1. Which one did you buy? 2. Where did you tap in for power? Switched/unswitched?
hondatrail125.com
Good to know. I'm only using it to charge my phone or GoPro so don't know if that will be an issue. RPMs will be fairly high most of the time which should be enough to keep them charged. I'll keep an eye on it and come up with a plan B if necessary. Hi - Just got my US 125 and was looking to...
hondatrail125.com
There are also several YouTube videos of people installing USB outlets on the CT125 that may be helpful for reference, just make sure they're working on USA model bikes.
Wiring diagram for the earlier USA model is at the back of the
service manual.
If the 2023's wiring looks much different Helm sells a service manual for the 2023:
https://www.helminc.com/helm/product2.asp?class_2=AHC&Sku=61K2E50&itemtype=N