If you wish to do auto repairs on your own Derbi 125 SM Baja then it will always be a good plan to have a Workshop Manual to use as a guide in case you need to know how to take off a certain part for example Drive Shaft and match it again appropriately.
Derbi 125 SM Baja Workshop Manuals are able to offer particular diagnostic information for the automobile so if something is broken it helps you identify what the issue is and ways to fix it. You will be able to analyse if this can be done yourself or that the job is simply too big it is possible to make a booking for your 125 SM Baja in with a suitable garage.
Derbi 125 SM Baja manual