If you have a YZF-R125/WR125/MT125 and you don’t have it already, please grab a PDF copy of the R125 service manual and owners manual from the links below. They’re only the first gen but there’s still a lot of similarities and most of the engine stuff is the same as on the WR/MT.

YZF-R125 Service manual

Covers most/all repair procedures, also includes a few pages with every torque value needed, wiring diagrams etc

YZF-R125 owner’s manual

Covers stuff like how to *actually* check the oil correctly, maintenance procedures…etc

YZF-R125 Error codes:

I’m not trying to claim credit for these – very useful post on the R125 forum:

https://www.r125forum.com/threads/error-code-list.8660/