If you wish to accomplish fixes for your Derbi Mulhacen 659 then it will always be a good plan to own a Workshop Manual to keep just for personal reference just in case you want to know tips to take off a certain component for example, the Gearbox and install it again safely.
Derbi Mulhacen 659 Workshop Manuals provide you with identifiable diagnostic wisdom on your vehicle so if something is not working it will help you determine what the situation is and how you can repair it. After that you can assess if this can be achieved yourself or in the event the job is just too big it is possible to book your Mulhacen 659 in with a decent repair garage.
Derbi Mulhacen 659 manual