If you choose to perform repairs on your own Kawasaki Z 400 G then it is usually a good plan to have access to a Workshop Manual to keep just for reference in case you need to know the way to remove a certain part for instance the Brake Discs and fit it again efficiently.
Kawasaki Z 400 G Workshop Manuals will give special diagnostic information with regards to your car so if something is playing up it will help you find out what the issue is and tips to fix it. After that you can determine if you can do this by yourself or that the job is too big you can actually make a reservation for your Z 400 G into a decent friendly mechanic.
Kawasaki Z 400 G manual