If you have to carry out maintenance on your Yamaha RD 400 then it will always be a good plan to possess a Workshop Manual to keep just for a guide should you need to know the best ways to take off a particular component for instance the Brake Discs and match it again perfectly.
Yamaha RD 400 Workshop Manuals are able to offer unique diagnostic wisdom on your car so if something is not working it will help you understand what the issue is and the way to repair it. After that you can evaluate if this can be done on your own or that the job is too big you can make a reservation for your RD 400 in with a suitable repair garage.
Yamaha RD 400 manual