Yamaha EF1000iS Service Manual page 62

CYLINDER (CRANKCASE 1) AND VALVE
a
4. Measure:
9 Valve spring tilt a
Out of specification → Replace.
Tilt limit:
2.0 mm (0.079 in)
5. Inspect:
9 Valve contact surface
More than 2/3 of the contact surface
does not contact → Replace.
3-32
ENG