If you want to accomplish maintenance to your Derbi Senda Baja 125 R then it is usually recommended to possess a Workshop Manual to use as reference if perhaps you want to know simple methods to remove a certain part much like the Brake Pads and match it again in the right way.
Derbi Senda Baja 125 R Workshop Manuals will provide you with certain diagnostic guidelines for the car so if something is wrong it helps you determine what the problem is and tips on how to repair it. After that you can analyse if this can be done yourself or in the event the job is too big you can actually make a reservation for your Senda Baja 125 R right into a suitable mechanic.
Derbi Senda Baja 125 R manual