If you need to accomplish maintenance for your Yamaha YZ 250 then it is always recommended to have a Workshop Manual to keep just for personal reference just in case you want to know the right way to remove a certain part much like the Gearbox and match it again accordingly.
Yamaha YZ 250 Workshop Manuals will provide you with precise diagnostic info with regards to your car so if something is not working it can help you ascertain what the issue is and tips to resolve it. Then you are able to assess if you can do this yourself or that the job is just too big you are able to make a reservation for your YZ 250 into a nearby mechanic.
Yamaha YZ 250 manual