Inspection
INSPECTION1. Check the cylinder head for cracks, damage and coolant leakage. If cracked, replace the cylinder head.
2. Remove scale, sealing compound and carbon deposits completely. After cleaning the oil passages, apply compressed air to verify that the passages are not clogged.
3. Check the cylinder head surface for flatness in the direction as shown in the illustration. If flatness exceeds service limit in any direction, either replace the cylinder head or machine the cylinder head matching surface lightly.
Flatness of cylinder head gasket surface
Standard: Less than 0.03 mm (0.0012 inch)
Limit: 0.2 mm (0.008 inch)
VALVES
1. Using a wire brush, clean the valve thoroughly.
2. Check each valve for wear, damage and distortion of the head and the stem at B Position. Replace, if necessary. If stem end, A, is hollowed out or worn, resurface as necessary. This correction must be limited to a minimum. Also resurface the valve face.
Replace the valve if the margin has decreased to less than the service limit.
Margin
[Standard]
Intake: 1.0 mm (0.040 inch)
Exhaust: 1.5 mm (0.059 inch)
[Limit]
Intake: 0.7 mm (0.028 inch)
Exhaust: 1.0 mm (0.040 inch)
VALVE SPRINGS
1. Check the free height of each valve spring. If they exceed the service limit, replace the springs.
2. Using a square, test the squareness of each spring. If a spring is excessively out-of-square, replace it.
Valve spring
[Standard]
Free height: 45.82 mm (1.804 inch)
Load: 23.3kg /40 mm (55.8 lbs. / 1.57 inch)
Out of square: 1.5° or less
[Limit]
Free height: 44.82 mm (1.7646 inch)
Out of square: 4°
VALVE GUIDES
Check the valve stem-to-guide clearance. If the clearance exceeds the service limit, replace the valve guide with the next oversize part.
Valve stem - to - guide clearance
[Standard]
Intake: 0.020 - 0.047 mm (0.0008 - 0.0020 inch)
Exhaust: 0.050 - 0.085 mm (0.0020 - 0.0033 inch)
[Limit]
Intake: 0.1 mm (0.0040 in)
Exhaust: 0.15 mm (0.0059 inch)
REPLACING THE VALVE SEAT RING
1. Cut away the inner face of the valve seat to reduce the wall thickness.
2. Enlarge the diameter of the valve seat so that it matches the specified oversize hole diameter of the new valve seat ring.
3. Heat the cylinder head to about 250°C (480°F) and press-fit an oversize seat ring for the bore in the cylinder head.
4. Using lapping compound, lap the valve to the new seat.
Valve seat contact width 0.9 - 1.3 mm (0.035 - 0.051 inch)
VALVE SEAT INSERT OVERSIZES