If you have to carry out adjustments to your Yamaha Zuma 125 then it will always be a great idea to own a Workshop Manual for a reference should you need to know how you can take off a specific component like the Gearbox and install it again accordingly.
Yamaha Zuma 125 Workshop Manuals offers you distinct diagnostic guides for the vehicle therefore if something is faulty it helps you understand what the issue is and some ways to correct it. You can then analyse if this can be done yourself or in case the job is simply too big you could make a booking for your Zuma 125 right into a local friendly mechanic.
Yamaha Zuma 125 manual