If you have to conduct repairs to your Suzuki GSR 400 then it will always be a good plan to have access to a Workshop Manual for reference if perhaps you want to know easy methods to remove a particular part for example the Brake Discs and match it again safely.
Suzuki GSR 400 Workshop Manuals can offer you special diagnostic details on your vehicle so if something is wrong it helps you understand what the issue is and ways to make it better. You can then analyse if this can be achieved yourself or that the job is simply too big you can book your GSR 400 in with a trusted friendly mechanic.
Suzuki GSR 400 manual