2004 Official factory service manual for Yamaha YFZ450S ATV Quad., Page 173Get this manual
CYLINDER AND PISTON
3Measure: piston ring end gap Out of specification Replace the piston ringNOTE: The oil ring expander spacer's end gap cannot be measuredIf the oil ring rail's gap is excessive, replace all three piston ringsPiston ring end gap Top ring 0.200.30 mm (0.0080.012 in) Limit: 0.55 mm (0.022 in) 2nd ring 0.350.50 mm (0.0140.020 in) Limit: 0.85 mm (0.034 in) Oil ring 0.200.50 mm (0.0080.020 in)