Intake/Exhaust Valves, Valve Guides - Yanmar 3YM30 Sevice Manual

5.2.3 Intake/exhaust valves, valve guides

(1) Wearing and corrosion of valve stem
Replace the valve stem is excessively worn or
corroded.
Valve stem
outside dia.
Intake 5.960-5.975
Exhaust 5.945-5.960
(2) Inspection of valve seat wear and contact surface
Inspect for valve seat scratches and excessive wear. Check to make sure the contact surface is normal.
The seat angle must be checked and adjusted if the valve seat contact surface is much smaller than the
width of the valve seat.
NOTE:
Keep in mind the fact that the intake and discharge valve have different diameters.
(3) Valve sink
Over long periods of use and repeated lapping,
combustion efficiency may drop. Measure the sinking
distance and replace the valve and valve seat if the
valve sink exceeds the tolerance.
Valve sink
Standard Limit
5.90
5.90
Standard Limit
0.4-0.6 0.8
5. Inspection and servicing of basic engine parts
30 mm
mm
mm
(Valve sink depth)
Depth micrometer
110
60 mm
Valve sinking depth
(Valve sink)