If you want to accomplish maintenance tasks to your Yamaha XT 125 R then it is usually a great idea to have a Workshop Manual to keep just for reference in case that you need to know how to strip off a specific component for instance the Wheel and install it again in the correct manner.
Yamaha XT 125 R Workshop Manuals can offer you particular diagnostic info for the car or truck therefore if something is broken it helps you understand what the issue is and tips to make it better. Then you are able to assess if this can be done on your own or if ever the job is just too big you could make a booking for your XT 125 R in with a decent friendly mechanic.
Yamaha XT 125 R manual