If you want to do repairs to your Honda CN 250 then it is always a great idea to have access to a Workshop Manual to keep just for a guide just in case you want to know the way to take off a specific component including Gearbox and match it again accordingly.
Honda CN 250 Workshop Manuals will provide you with unique diagnostic guides for the vehicle so if something is playing up it can help you work out what the situation is and how you can correct it. You will be able to decide if this can be done by yourself or if the job is simply too big you could make a booking for your CN 250 into a decent repair garage.
Honda CN 250 manual