If you want to do adjustments on your own Vespa PX 125 then it is always recommended to possess a Workshop Manual to use as a guide just in case you want to know how to strip off a specific part for instance the Clutch and fit it again accurately.
Vespa PX 125 Workshop Manuals offer you distinct diagnostic guides for your automobile so if something is not working it helps you ascertain what the problem is and tips to fix it. After that you can analyse if this can be achieved by yourself or if the job is simply too big it is possible to book your PX 125 right into a decent garage.
Vespa PX 125 manual