If you wish to carry out maintenance tasks on your own Yamaha RD 125 then it is usually recommended to have access to a Workshop Manual for a guide just in case you want to know the best ways to strip off a certain part for instance the Brake Discs and fit it again safely.
Yamaha RD 125 Workshop Manuals provides specific diagnostic facts on your automobile so if something is playing up it will help you determine what the issue is and methods to repair it. You can then assess if you can do this on your own or if the job is just too big it is possible to make a reservation for your RD 125 in to a suitable car garage.
Yamaha RD 125 manual