Inspection
CYLINDER HEAD DISTORTION
- Clean surface of cylinder head.
- Use a reliable straightedge and feeler gauge to check the flatness of cylinder head surface.
- Check along six positions shown in image.
Head surface flatness:
Standard: Less than 0.03 mm (0.0012 inch)
Limit: 0.1 mm (0.004 inch)
If beyond the specified limit, replace or resurface.
Resurfacing limit:
The limit for cylinder head resurfacing is determined by the cylinder block resurfacing.
Amount of cylinder head resurfacing is "A".
Amount of cylinder block resurfacing is "B".
The maximum limit is as follows:
A + B = 0.2 mm (0.008 inch)
After resurfacing cylinder head, check that camshaft rotates freely by hand If resistance is felt, cylinder head must be replaced.
Nominal cylinder head height: 126.3 - 126.5 mm (4.972 - 4.980 inch)
CAMSHAFT VISUAL CHECK
Check camshaft for scratches, seizure and wear.
CAMSHAFT RUNOUT
1. Measure camshaft runout at the center journal.
Runout (Total indicator reading):
Standard: Less than 0.02 mm (0.0008 inch)
Limit: 0.04 mm (0.0016 inch)
2. If it exceeds the limit, replace camshaft.
CAMSHAFT CAM HEIGHT
1. Measure camshaft cam height.
Standard cam height:
Intake: 42.505 - 42.695 mm (1.6734 - 1.6809 inch)
Exhaust: 40.905 - 41.095 mm (1.6104 - 1.6179 inch)
Cam wear limit:
Intake & Exhaust: 0.2 mm (0.008 inch)
2. If wear is beyond the limit, replace camshaft.
CAMSHAFT JOURNAL CLEARANCE
1. Install camshaft brackets and tighten bolts to the specified torque.
2. Measure inner diameter of camshaft bearing.
Standard inner diameter:
# 1 to # 5 journals: 28.000 - 28.025 mm (1.1024 - 1.1033 inch)
3. Measure outer diameter of camshaft journal.
Standard outer diameter:
# 1 to # 5 journals: 27.935 - 27.955 mm (1.0998 - 1.1006 inch)
4. If clearance exceeds the limit, replace camshaft and/or cylinder head.
Camshaft journal clearance:
Standard: 0.045 - 0.090 mm (0.0018 - 0.0035 inch)
Limit: 0.12 mm (0.0047 inch)
CAMSHAFT END PLAY
1. Install camshaft in cylinder head.
2. Measure camshaft endplay.
Camshaft endplay:
Standard: 0.070 - 0.148 mm (0.0028 - 0.0058 inch)
Limit: 0.20 mm (0.0079 inch)
3. If endplay exceeds the limit, replace camshaft and remeasure camshaft endplay.
4. If endplay still exceeds the limit after replacing camshaft, replace cylinder head.
CAMSHAFT SPROCKET RUNOUT
1. Install sprocket on camshaft.
2. Measure camshaft sprocket runout.
Runout (Total indicator reading): Limit 0.12 mm (0.0047 inch)
3. If it exceeds the limit, replace camshaft sprocket.
VALVE GUIDE CLEARANCE
1. Measure valve deflection as shown in image. (Valve and valve guide mostly wear in this direction.)
Valve intake and exhaust deflection limit (Dial gauge reading): 0.2 mm (0.008 inch)
2. If it exceeds the limit, check valve to valve guide clearance.
a. Measure valve stem diameter and valve guide inner diameter.
b. Check that clearance is within specification.
Valve to valve guide clearance = Valve guide inner diameter - Valve stem diameter:
c. If it exceeds the limit, replace valve and remeasure clearance.
- If clearance still exceeds the limit after replacing valve, replace the valve guide.
VALVE GUIDE REPLACEMENT
1. To remove valve guide, heat cylinder head to 120 to 140° C (248 to 284° F).
2. Drive out valve guide using a hammer and suitable tool or a press [under a 20 kN (2 ton, 2.2 US ton, 2.0 Imp ton) pressure].
3. Ream cylinder head valve guide hole.
Valve guide hole diameter (for service parts):
Intake & Exhaust: 11.175 - 11.196 mm (0.4400 - 0.4408 inch)
4. Heat cylinder head to 120 to 140° C (248 to 284° F) and press service valve guide onto cylinder head.
Projection "L": 13.3 - 13.9 mm (0.524 - 0.547 inch)
5. Ream valve guide. Finished size:
Intake & Exhaust: 7.000 - 7.018 mm (0.2756 - 0.2763 inch)
VALVE SEATS
Check valve seats for pitting at contact surface. Resurface or replace if excessively worn.
- Before repairing valve seats, check valve and valve guide for wear. If they are worn, replace them. Then correct valve seat.
- Use both hands to cut uniformly.
REPLACING VALVE SEAT FOR SERVICE PARTS
1. Bore out old seat until it collapses. Set machine depth stop so that boring cannot contact bottom face of seat recess in cylinder head.
2. Ream cylinder head recess.
Reaming bore for service valve seat
Oversize [0.5 mm (0.020 inch)]:
Intake: 38.000 - 38.016 mm (1.4961 - 1.4967 inch)
Exhaust: 32.700 - 32.716 mm (1.2874 - 1.2880 inch)
- Use the valve guide center for reaming to ensure valve seat will have the correct fit.
3. Heat cylinder head to 120 to 140° C (248 to 284° F).
4. Press fit valve seat until it seats on the bottom.
5. Cut or grind valve seat using suitable tool to the specified dimensions.
6. After cutting, lap valve seat with abrasive compound.
7. Check valve seating condition.
Seat face angle "a": 44�53' ~ 45�07'
Contacting width "W":
Intake: 1.48 - 1.63 mm (0.0583 - 0.0642 inch)
Exhaust: 1.8 - 2.0 mm (0.071 - 0.079 inch)
VALVE DIMENSIONS
Check dimensions of each valve.
When valve head has been worn down to 0.5 mm (0.020 inch) in margin thickness, replace valve.
Grinding allowance for valve stem tip is 0.2 mm (0.008 inch) or less.
VALVE SPRING
Squareness
1. Measure dimension "S".
Out-of-square "S": Less than 2.2 mm (0.087 inch)
2. If it exceeds the limit, replace spring.
Pressure
Check valve spring pressure at specified spring height.
Pressure:
Standard: 418.0 N (42.64 kg, 93.97 lbs.) at 29.17 mm (1.1484 inch)
Limit: More than 393.0 N (40.09 kg, 88.35 lbs.) at 29.17 mm (1.1484 inch)
If it exceeds the limit, replace spring.
VALVE LIFTER AND VALVE SHIM
1. Check contact and sliding surfaces for wear or scratches.
2. Check diameter of valve lifter and valve lifter guide bore.
Valve lifter diameter: 33.960 - 33.975 mm (1.3370 - 1.3376 inch)
Lifter guide bore diameter: 34.000 - 34.021 mm (1.3386 - 1.3394 inch)
Valve lifter to valve lifter guide clearance: 0.025 - 0.061 mm (0.0010 - 0.0024 inch)
If it exceeds the standard diameter or clearance, replace valve lifter or cylinder head.