2004 Official factory service manual for Yamaha YFZ450S ATV Quad., Page 174Get this manual
CYLINDER AND PISTON
2Measure: piston pin outside diameter Out of specification Replace the piston pinPiston pin outside diameter 19.99120.000 mm (0.78700.7874 in) Limit: 19.971 mm (0.786 in) 3Measure: piston pin bore inside diameter Out of specification Replace the pistonPiston pin bore inside diameter 20.00420.015 mm (0.78760.7880 in) Limit: 20.045 mm (0.789 in)