If you choose to execute maintenance tasks on your own Hercules K 125 S then it will always be recommended to have a Workshop Manual to use as personal reference if you need to know methods to strip off a particular part for example, the Drive Shaft and fit it again correctly.
Hercules K 125 S Workshop Manuals can offer you detailed diagnostic wisdom with regards to your car or truck so if something is playing up it will help you understand what the issue is and how you can fix it. After that you can determine if this can be achieved on your own or if the job is simply too big you can actually book your K 125 S in to a suitable garage.
Hercules K 125 S manual