2007 Yamaha Apex Factory Service Manual, Page 206Get this manual

2007 Yamaha Apex Factory Service Manual, Page 206

CRANKCASE 4Install: Piston ring (into the cylinder) NOTE: Level the piston ring in the cylinder with the piston crowna mm
gap: Top ring 0.32 0.44 mm (0.010 0.020 in) 2nd ring 0.43 0.58 mm (0.017 0.023 in) Oil ring 0.10 0.35 mm (0.004 0.014 in)
6Inspect: Piston pin Blue discolorationgroovesReplace the piston pin and then check the lubrication system 7Measure: Outside