Inspection
INSPECTIONCylinder Head
1. Before cleaning, check the cylinder head for water leaks, gas leaks, damage and cracks.
2. Remove oil, scale, sealing compound and carbon deposit completely. After cleaning oil passages, apply compressed air to ensure that the passages are not clogged.
3. Check the cylinder head gasket surface for flatness by using a straight edge and a feeler gauge.
If the service limit is exceeded, correct to meet specifications.
Standard value: 0.03 mm (0.0012 inch) or less
Limit: 0.2 mm (0.008 inch)
Grinding limit: 0.2 mm (0.008 inch)
Cylinder head height: 119.9-120.1 mm (4.72-4.73 inch)
Caution: The total thickness of the surface allowed to be removed from cylinder head and mating cylinder block is 0.2 mm (0.0079 inch) in thickness.
Valve
1. Check the valve face for correct contact. If incorrect, reface using a valve refacer. Valve should make a uniform contact with the seat at the center of valve face.
2. If the margin exceeds the service limit replace the valve.
Standard value:
Intake 1.0 mm (0.039 inch)
Exhaust 1.2 mm (0.047 inch)
Limit:
Intake 0.5 mm (0.019 inch)
Exhaust 0.7 mm (0.028 inch)
3. Measure the valve's total length.
If the measurement is less than specified, replace the valve.
Valve Springs
1. Measure the free height of the spring and, if it is smaller than the limit, replace.
Standard value: 51.0 mm (2.01 inch)
Limit: 50.0 mm (1.97 inch)
2. Measure the squareness of the spring and, if the limit is exceeded, replace.
Standard value: 20 or less
Limit: Max. 40
Valve Guides
1. Measure the clearance between the valve guide and valve stem. If the limit is exceeded, replace the valve guide or valve, or both.
Standard value:
Intake 0.02-0.05 mm (0.0008-0.0020 inch)
Exhaust 0.04-0.07 mm (0.0016-0.0028 inch)
Limit:
Intake 0.10 mm (0.004 inch)
Exhaust 0.15 mm (0.006 inch)
Valve Seat
1. Assemble the valve, then measure the valve stem projection between the end of the valve stem and the spring seating surface. If the measurement exceeds the specified limit, replace the valve seat.
Standard value: 49.30 mm (1.9409 inch)
Limit: 49.80 mm (1.9606 inch)
Valve Seat Reconditioning Procedure
1. Before correcting the valve seat, check for clearance between the valve guide and valve and, if necessary, replace the valve guide.
2. Using the special tool or seat grinder, correct to obtain the specified seat width and angle.
3. After correcting the valve seat, lap the valve and valve seat using lapping compound. Then, check the valve stem projection.
Valve Seat Replacement Procedure
1. Cut the valve seat to be replaced from the inside to thin the wall thickness. Then, remove the valve seat.
2. Rebore the valve seat hole in the cylinder head to a selected oversize valve seat diameter.
Intake valve seat ring hole:
0.3 O.S.: 34.30-34.33 mm (1.3504-1.3516 inch)
0.6 O.S.: 34.60-34.63 mm (1.3622-1.3634 inch)
Exhaust valve seat ring hole:
0.3 O.S.: 31.80-31.83 mm (1.2520-1.2531 inch)
0.6 O.S.: 32.10-32.13 mm (1.2638-1.2650 inch)
3. Before fitting the valve seat, either heat the cylinder head up to approximately 250°C (482°F) or cool the valve seat in liquid nitrogen, to prevent the cylinder head bore from galling.
4. Using a valve seat cutter, correct the valve seat to the specified width and angle.
5. See "VALVE SEAT RECONDITIONING PROCEDURE".
Valve Guide Replacement Procedure
1. Remove the snap ring from the exhaust valve guide.
2. Using the press, remove the valve guide toward the cylinder block.
3. Rebore the valve guide hole of the cylinder head so that it fits the press-fitted oversize valve guide.
Caution: Do not install a valve guide of the same size again.
Valve guide hole:
0.05 O.S.: 11.05-11.07 mm (0.4350-0.4358 inch)
0.25 O.S.: 11.25-11.27 mm (0.4429-0.4437 inch)
0.50 O.S.: 11.50-11.52 mm (0.4528-0.4535 inch)
4. Install the new snap ring into groove of exhaust valve guide.
5. Press-fit the valve guide until it protrude 14.0 mm (0.551 inch) from the cylinder head top surface as shown in the illustration.
NOTE:
1. When press-fitting the valve guide, work from the cylinder head top surface.
2. Pay attention to the difference in length of the valve guides. [intake side: 45.5 mm (1.79 inch); exhaust side: 50.5 mm (1.99 inch)].
3. After installing the valve guides, insert new valves in them to check for sliding condition.