If you choose to accomplish fixes to your Yamaha SR 125 then it will always be a good idea to own a Workshop Manual to keep just for a guide should you want to know the way to take off a particular part for example Exhaust and install it again in the correct way.
Yamaha SR 125 Workshop Manuals offers clear exact diagnostic guides on your vehicle so if something is wrong it helps you ascertain what the problem is and methods to correct it. You can then evaluate if this can be achieved yourself or that the job is simply too big it is possible to make a reservation for your SR 125 in with a decent garage.
Yamaha SR 125 manual