1998-2006 Yamaha F20/F25 Outboards Service Manual, Page 163Get this manual
IpOWRt21: I
CAMSHAFT AND VALVES
SERVICE POINTS
Valve inspection 1Measure: Valve guide bore Out of specification valve guideValve guide bore limit: 5.5005.512 mm (0.21650.2170 in) 2Measure: Valve seat width Out of specification valve seat
Replace the
Reface the
Valve seat width limit: 0.91.1 mm (0.0350.043 in)
3 Measure: Margin thickness Out of specification valveMargin thickness: IN: 0.61.0 mm (0.0240.039 in) EX: 0.71.1 mm (0.0280.043 in) 4Measure: Valve stem diameter Out of specification valve