If you wish to carry out fixes to your Honda CRF450R then it will always be a good idea to have access to a Workshop Manual for personal reference if you want to know proven methods to take out a particular part for instance the Drive Shaft and match it again efficiently.
Honda CRF450R Workshop Manuals will give you precise diagnostic info on your vehicle so if something is playing up it helps you ascertain what the situation is and how to resolve it. After that you can analyse if this can be done yourself or that the job is just too big you can make a reservation for your CRF450R right into a decent mechanic.
Honda CRF450R manual