If you have to conduct maintenance for your Yamaha SR 400 then it is usually recommended to own a Workshop Manual to keep just for reference just in case you need to know simple methods to take out a specific component for example Brake Pads and match it again efficiently.
Yamaha SR 400 Workshop Manuals gives you distinct diagnostic guidelines with regards to your automobile therefore if something is not working it helps you figure out what the problem is and how you can make it better. You will be able to analyse if this can be achieved on your own or in the event the job is simply too big you can actually book your SR 400 in to a trusted repair garage.
Yamaha SR 400 manual