If you have to carry out adjustments for your GAS GAS EC125 then it will always be recommended to have a Workshop Manual to use as reference if perhaps you need to know the best ways to take off a particular component much like the Drive Shaft and match it again properly.
GAS GAS EC125 Workshop Manuals can offer you exact diagnostic details on your vehicle so if something is broken it helps you figure out what the issue is and methods to correct it. You can then assess if this can be done by yourself or if the job is too big you can actually book your EC125 right into a decent car garage.
GAS GAS EC125 manual