Cylinder Head Assembly: Testing and Inspection

Cylinder head





1. Check the cylinder head for cracks, damage and coolant leakage. If cracked, replace the cylinder head.





2. Remove scale, sealing compound and carbon. After cleaning oil passages, apply compressed air to ensure that passages are not clogged.
3. Check the cylinder head surface for flatness in the direction of A, B. as shown in illustration. If flatness exceeds service limit in any direction, either replace the cylinder head, or lightly machine the cylinder head gasket surface.

Standard value:
Cylinder head surface flatness:
Less than 0.005 mm (0.002 inch)
Limit:
Cylinder head surface flatness: 0.1 mm (0.0040 inch)

Valves





1. Using a wire brush, clean the valve thoroughly.





2. Check each valve for wear, damage and distortion of head and stem at B. Repair or correct, if necessary. If stem end A is pitted 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 value:
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 valve spring free length and tension. If they exceed the service limit, replace the spring.
2. Using a square, test the squareness of each spring. If a spring is excessively out of square, replace it.

Valve Spring:
Standard value:
Free height: 48.3 mm (1.902 inch)
Load: 300N (66 lbs.) 40 mm (1.575 inch)
Out of square: Less than 1.5°
Limit:
Free height: -1.0 mm (-0.039 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 value:
Intake: 0.020 - 0.047 mm (0.0008 - 0.0019 inch)
Exhaust: 0.050 - 0.085 mm (0.0020 - 0.0033 inch)
Limit:
Intake: 0.1 mm (0.0040 inch)
Exhaust: 0.15 mm (0.0059 inch)

Valve Seat Insert





Check the valve seat for evidence of overheating and improper contact with the valve face. Recondition or replace the seat if necessary.

Before reconditioning the seat, check the valve guide for wear. if the valve guide is worn, replace it, then recondition the seat. Recondition the valve seat with a valve seat grinder or cutter. The valve seat contact width should be within specifications and centered on the valve face.