If you choose to accomplish repairs to your Honda XL 250 S then it is always a good idea to possess a Workshop Manual for personal reference should you need to know the way to take out a certain component like the Gearbox and match it again in the correct manner.
Honda XL 250 S Workshop Manuals will give you specific diagnostic info on your vehicle therefore if something is broken it will help you ascertain what the issue is and some ways to resolve it. After that you can determine if this can be achieved yourself or that the job is simply too big you can actually book your XL 250 S in with a local mechanic.
Honda XL 250 S manual