If you choose to carry out adjustments on your own Honda CBF250 then it is always recommended to have a Workshop Manual to use as a reference in case that you want to know methods to strip off a specific component for instance the Gearbox and install it again successfully.
Honda CBF250 Workshop Manuals offer you certain diagnostic details for the car or truck so if something is playing up it helps you determine what the issue is and the way to resolve it. After that you can evaluate if this can be achieved by yourself or if ever the job is too big you can actually book your CBF250 into a decent garage.
Honda CBF250 manual