If you wish to do maintenance tasks for your Honda CB 125 disc then it is usually a good idea to own a Workshop Manual to use as a reference in the event you want to know tips to strip off a particular part including Brake Discs and match it again adequately.
Honda CB 125 disc Workshop Manuals offer you specific diagnostic information for your vehicle therefore if something is broken it can help you figure out what the situation is and how you can fix it. After that you can decide if this can be achieved yourself or in the event the job is too big you could make a reservation for your CB 125 disc into a trusted mechanic.
Honda CB 125 disc manual