If you choose to do adjustments for your CCM 644 DS Dual Sport then it is usually a good plan to possess a Workshop Manual to use as reference in case that you want to know tips on how to remove a particular component such as the Gearbox and match it again correctly.
CCM 644 DS Dual Sport Workshop Manuals will give you exact diagnostic info on your car therefore if something is playing up it will help you figure out what the problem is and the way to repair it. After that you can assess if you can do this yourself or if the job is too big you can actually book your 644 DS Dual Sport into a decent friendly mechanic.
CCM 644 DS Dual Sport manual