G424 Service Manual Base Engine Service Procedure141
6EN0542
1EN0264
1EN0279
2. Valve
(1) Check the valve face for correct contact. If incorrect,
reface. Valve seat contact should be maintained uniform
at the center of valve face.
(2) If the margin exceeds the service limit, replace the valve:
Standard value:
Intake 1.2 mm (0.047 in.)
Exhaust 2.0 mm (0.079 in.)
Limit:
Intake 0.7 mm (0.028 in.)
Exhaust 1.5 mm (0.059 in.)
(3) Measure the valve’s total length. If the measurement is
less than specified, replace the valve.
Standard value:
Intake 106.6 mm (4.197 in.)
Exhaust 105.2 mm (4.142 in.)
Limit:
Intake 106.1 mm (4.177 in.)
Exhaust 104.7 mm (4.122 in.)
3. Valve Spring
(1) Measure the free height of spring and, if it is smaller than
the limit, replace.
Standard value: 48.0 mm (1.89 in.)
Limit: 47.0 mm (1.85 in.)
(2) Measure the squareness of the spring and, if the limit is
exceeded, replace.
Standard value: 2 degrees or less
Limit: 4 degrees
4. Valve Guide
Measure the clearance between the valve guide and valve
stem. If the limit is exceeded, replace the valve guide or
valve, or both.
Margin
Valve seat
contact
Free height
Out of squareness
Valve
guide
Guide I.D.
Stem I.D.
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