Yamaha's factory service manual for the 2014 YZ125 is part number LIT-11626-27-06. The bike is model code YZ125E2, and coverage is limited to that season.
Later YZ manuals are laid out for speed of use. Specifications sit in tables you can find without reading around them, tightening torques appear with the assemblies they belong to, and the periodic maintenance chapter gives intervals along with the procedure for each item. Engine, chassis, fuel system, ignition, suspension and electrics are all treated as the factory treated them.
If the bike has been raced, and most have, start in the inspection material. It tells you what to measure and what the limit is, so a rebuild is decided on numbers. Check YZ125E2 on the frame label before ordering; adjacent model years have their own part numbers and their own figures.
