If you choose to carry out maintenance tasks on your CZ 250 Twin then it will always be recommended to have access to a Workshop Manual to keep just for reference should you need to know methods to take out a particular component like the Gearbox and fit it again perfectly.
CZ 250 Twin Workshop Manuals will give targeted diagnostic details for your vehicle therefore if something is broken it can help you discover what the problem is and methods to repair it. You can then assess if you can do this yourself or in the event the job is just too big you can still book your 250 Twin in with a nearby mechanic.
CZ 250 Twin manual