1. Check for cracks or damage. Use liquid penetrant tester on the important sections to check for fissures. Check that there are no marks of gas leaking or water leaking on gasket installing surface.
2. Place the cylinder head on the ST.
| ST 498267800 | CYLINDER HEAD TABLE |
3. Measure the warping of the cylinder head surface that mates with cylinder block using a straight edge (A) and thickness gauge (B).
If the warping exceeds the limit, correct the surface by grinding it with a surface grinder.
Warping limit:
0.035 mm (0.0014 in)
Grinding limit:
0.1 mm (0.004 in)
Standard height of cylinder head:
97.5 mm (3.839 in)
NOTE:
Uneven torque for the cylinder head bolts can cause warping. When reassembling, pay special attention to the torque so as to tighten evenly.
Inspect the intake and exhaust valve seats, and correct the contact surfaces with a valve seat cutter if they are defective or when valve guides are replaced.
Valve seat width W:
Standard:
Intake (A)
0.8 — 1.4 mm (0.03 — 0.055 in)
Exhaust (B)
1.2 — 1.8 mm (0.047 — 0.071 in)
1. Check the clearance between valve guide and valve stem. The clearance can be checked by measuring respectively the outer diameter of valve stem with a micrometer and the inner diameter of valve guide with a caliper gauge.
Clearance between the valve guide and valve stem:
Standard:
Intake
0.035 — 0.062 mm (0.0014 — 0.0024 in)
Exhaust
0.040 — 0.067 mm (0.0016 — 0.0026 in)
|
(A) |
Valve guide |
2. If the clearance between the valve guide and valve stem exceeds the standard, replace the valve guide or valve itself, whichever shows greater amount of wear or damage. See the following procedure for valve guide replacement.
Valve guide inner diameter:
6.000 — 6.012 mm (0.2362 — 0.2367 in)
Valve stem outer diameters:
Intake
5.950 — 5.965 mm (0.2343 — 0.2348 in)
Exhaust
5.945 — 5.960 mm (0.2341 — 0.2346 in)
(1) Place the cylinder head on ST1 with the combustion chamber upward so that valve guides fit the holes in ST1.
(2) Insert the ST2 into valve guide and press it down to remove the valve guide.
| ST1 498267800 | CYLINDER HEAD TABLE |
| ST2 499767200 | VALVE GUIDE REMOVER |
(3) Turn the cylinder head upside down and place the ST as shown in the figure.
| Intake side |
| ST 499767700 | VALVE GUIDE ADJUSTER |
| Exhaust side |
| ST 499767800 | VALVE GUIDE ADJUSTER |
|
(A) |
Valve guide |
(4) Before installing a new valve guide, make sure that neither scratches nor damages exist on the inner surface of valve guide holes in cylinder head.
(5) Put a new valve guide, coated with sufficient oil, in cylinder, and insert the ST1 into valve guide. Press in until the valve guide upper end is flush with the upper surface of ST2.
| ST1 499767200 | VALVE GUIDE REMOVER |
| Intake side |
| ST2 499767700 | VALVE GUIDE ADJUSTER |
| Exhaust side |
| ST2 499767800 | VALVE GUIDE ADJUSTER |
(6) Check the valve guide protrusion.
Valve guide protrusion L:
Intake
20.0 — 21.0 mm (0.787 — 0.827 in)
Exhaust
16.5 — 17.5 mm (0.650 — 0.689 in)
|
(A) |
Valve guide |
(7) Ream the inside of valve guide using ST. Put the ST in valve guide, and rotate the ST slowly clockwise while pushing it lightly. Bring the ST back while rotating it clockwise.
NOTE:
• Apply engine oil to the ST when reaming.
• If the inner surface of valve guide is damaged, the edge of ST should be slightly ground with oil stone.
• If the inner surface of valve guide becomes lustrous and the ST does not chip, use a new ST or remedy the ST.
| ST 499767400 | VALVE GUIDE REAMER |
(8) After reaming, clean the valve guide to remove chips.
(9) Recheck the contact condition between valve and valve seat after replacing the valve guide.
1. Inspect the flange and stem of valve, and replace the valve with a new part if damaged, worn, deformed, or if dimension “H” in the figure is outside of the specified limit.
Head edge thickness H:
Intake (A)
Standard:
0.8 — 1.2 mm (0.03 — 0.047 in)
Exhaust (B)
Standard:
1.0 — 1.4 mm (0.039 — 0.055 in)
2. Put a small amount of grinding compound on the seat surface, and lap the valve and seat surface. Replace with a new valve oil seal after lapping.
NOTE:
It is possible to differentiate between the intake valve and the exhaust valve by their overall length.
Valve overall length:
Intake
120.6 mm (4.75 in)
Exhaust
121.7 mm (4.79 in)
1. Check the valve springs for damage, free length, and tension. Replace the valve spring if it is not within the standard value presented in the table.
2. To measure the squareness of the valve spring, stand the spring on a surface plate and measure its deflection at the top of spring using a try square.
|
Free length |
mm (in) |
55.2 (2.173) |
|
Tension/spring height N (kgf, lbf)/mm (in) |
Set |
235.3 — 270.7 (24 — 27.6, 52.9 — 60.8)/45.0 (1.772) |
|
Lift |
578.9 — 639.9 (59.1 — 65.3, 130.3 — 143.9)/34.7 (1.366) | |
|
Squareness |
2.5°, 2.4 mm (0.094 in) or less | |
6. INTAKE AND EXHAUST VALVE OIL SEAL
1. For the following, replace the oil seal with a new part.
See the procedure 2) and subsequent for replacement procedures.
• When the lip is damaged.
• When the spring is out of the specified position.
• When readjusting the surfaces of valve and valve seat.
• When replacing the valve guide.
2. Place the cylinder head on ST1, and use ST2 to press-fit the oil seal.
| ST1 498267800 | CYLINDER HEAD TABLE |
| ST2 498857100 | VALVE OIL SEAL GUIDE |
NOTE:
• Apply engine oil to oil seal before press-fitting.
• When press-fitting the oil seal, do not use a hammer or strike in.
• The intake valve oil seals and exhaust valve oil seals are distinguished by their colors.
Color of rubber part:
Intake [Gray]
Exhaust [Green]
