If you want to do maintenance to your Yamaha BWs 12inch then it is usually a great idea to own a Workshop Manual to keep just for a guide in case you need to know easy methods to strip off a particular component for example Drive Shaft and install it again properly.
Yamaha BWs 12inch Workshop Manuals offers you certain diagnostic information on your automobile therefore if something is broken it will help you understand what the problem is and how you can correct it. After that you can decide if this can be achieved yourself or in case the job is just too big you can actually book your BWs 12inch in to a decent mechanic.
Yamaha BWs 12inch manual