If you need to carry out maintenance tasks for your Yamaha TT R125 then it is always recommended to own a Workshop Manual to use as reference in case you need to know ways to take off a particular component for example, the Brake Discs and install it again accurately.
Yamaha TT R125 Workshop Manuals gives you specific diagnostic wisdom for the automobile therefore if something is playing up it can help you ascertain what the problem is and how you can make it better. After that you can decide if this can be done yourself or in the event the job is too big you are able to make a reservation for your TT R125 into a suitable repair garage.
Yamaha TT R125 manual