Inspection
CYLINDER HEAD DISTORTIONClean 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 the figure.
Head surface flatness: Limit 0.1 mm (0.004 inch)
If beyond the specified limit, resurface or replace it.
The limit for cylinder head resurfacing is determined by the cylinder block resurfacing.
Resurfacing limit:
Amount of cylinder head resurfacing is "A".
Amount of cylinder block resurfacing is "B".
The maximum limit: 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 A and B as shown in the figure.
Runout (Total indicator reading):
Limit 0.05 mm (0.0020 inch)
2. If it exceeds the limit, replace camshaft.
CAMSHAFT HEIGHT
1. Measure camshaft cam height.
Standard cam height: 43.940 - 44.130 mm (1.7299 - 1.7374 inch)
Cam wear limit: 0.2 mm (0.008 inch)
2. If wear is beyond the limit, replace camshaft.
CAMSHAFT JOURNAL CLEARANCE
1. Install camshaft bracket and tighten bolts to the specified torque.
2. Measure inner diameter "A" of camshaft bearing.
Inner diameter:
No. 1: 26.000 - 26.021 mm (1.0236 - 1.0244 inch)
No. 2,3,4: 23.500 - 23.521 mm (0.9252 - 0.9260 inch)
3. Measure outer diameter of camshaft journal.
Standard outer diameter:
No. 1: 25.935 - 25.955 mm (1.0211 - 1.0218 inch)
No. 2, 3, 4: 23.435- 23.455 mm (0.9226 - 0.9234 inch)
4. If clearance exceeds the limit, replace camshaft and/or cylinder head.
Camshaft journal clearance:
Standard: 0.045 - 0.086 mm (0.0018 - 0.0034 inch)
Limit: 0.15 mm (0.0059 inch)
CAMSHAFT END PLAY
1. Install camshaft in cylinder head.
2. Measure camshaft end play.
Camshaft end play:
Standard: 0.115 - 0.188 mm (0.0045 - 0.0074 inch)
Limit: 0.24 mm (0.0094 inch)
CAMSHAFT SPROCKET RUNOUT
1. Install sprocket on camshaft.
2. Measure camshaft sprocket runout.
Runout (Total indicator reading): Less than 0.15 mm (0.0059 inch)
If it exceeds the limit, replace camshaft sprocket.
VALVE GUIDE CLEARANCE
1. Measure valve deflection as shown in the figure. (Valve and valve guide mostly wear in this direction.)
Valve deflection limit (Dial gauge reading):
Intake: 0.24 mm (0.0094 inch)
Exhaust: 0.28 mm (0.0110 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 limit:
Intake: 0.08 mm (0.0031 inch)
Exhaust: 0.1 mm (0.004 inch)
c. If it exceeds the limit, replace valve or valve guide.
VALVE GUIDE REPLACEMENT
1. To remove valve guide, heat cylinder head to 110 to 130°C (230 to 266°F) by soaking in heated oil.
2. Drive out valve guide with a press [under a 20 kN (2 ton, 2.2 US ton, 2.0 Imp ton) pressure] or hammer and suitable tool.
3. Ream cylinder head valve guide hole.
Valve guide hole diameter (for service parts): 10.185 - 10.196 mm (0.4010 - 0.4014 inch)
4. Heat cylinder head to 110 to 130°C (230 to 266°F) and press service valve guide onto cylinder head.
Projection " L": 12.6 - 12.8 mm (0.496 - 0.504 inch)
5. Ream valve guide.
Finished size: 6.000 - 6.018 mm (0.2362 - 0.2369 inch)
VALVE SEATS
Check valve seats for any evidence of pitting at valve contact surface, and reseat or replace if it has worn out excessively.
- Before repairing valve seats, check valve and valve guide for wear. If they have 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. Boring should not continue beyond the bottom face of the seat recess in cylinder head. Set the machine depth stop to ensure this.
2. Ream cylinder head recess for service valve seat.
Oversize [0.5 mm (0.020 inch)]:
Intake: 37.500 - 37.516 mm (1.4764 - 1.4770 inch)
Exhaust: 32.700 - 32.716 mm (1.2874 - 1.2880 inch)
Be sure to ream in circles concentric to the valve guide center.
This will enable valve seat to fit correctly.
3. Heat cylinder head to 110 to 130°C (230 to 266°F) by soaking in heated oil.
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', deg
Contacting width "W":
Intake: 1.09 - 1.31 mm (0.0429 - 0.0516 inch)
Exhaust: 1.29 - 1.51 mm (0.0508 - 0.0594 inch)
8. Use a depth gauge to measure the distance between the mounting surface of the cylinder head spring seat and the valve stem end. If the distance is shorter than specified, repeat step 5 above to adjust it. If it is longer, replace the valve seat with a new one.
Valve seat resurface limit "L":
Intake: 41.07 - 41.67 mm (1.6169 - 1.6405 inch)
Exhaust: 40.06 - 41.60 mm (1.5772 - 1.6378 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 2.0 mm (0.079 inch)
2. If it exceeds the limit, replace spring.
Pressure
Check valve spring pressure at specified spring height.
Pressure:
Standard: 454 N (46.3 kg, 102.1 lbs) at height 27.55 mm (1.0846 inch)
Limit: More than 427 N (43.6 kg, 96.0 lbs)at height 27.55 mm (1.0846 inch)
If it exceeds the limit, replace spring.
VALVE LIFTER
1. Check contact and sliding surfaces for wear or scratches.
2. Check diameter of valve lifter and valve lifter guide bore.
Valve lifter outer diameter: 34.960 - 34.975 mm (1.3764 - 1.3770 inch)
Lifter guide bore diameter: 35.000 - 35.021 mm (1.3780 - 1.3788 inch)