Service Limits & General Specifications

Inspection after Disassembly

VALVE GUIDE CLEARANCE





1. Measure valve deflection as shown in figure. (Valve and valve guide wear the most in this direction.)
Valve deflection limit (dial gauge reading)
Intake & Exhaust: 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. Calculate valve to valve guide clearance.
Valve stem to valve guide clearance = valve guide inner diameter - valve stem diameter.





c. Check that clearance is within specification.
- If it exceeds the limit, replace valve and remeasure clearance.
- If limit is still exceeded after replacing valve, replace valve guide.

VALVE GUIDE REPLACEMENT





1. To remove valve guide, heat cylinder head to 110° to 130°C (230° to 266°F).





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)
Intake & Exhaust: 9.685 - 9.696 mm (0.3813 - 0.3817 inch)





4. Heat cylinder head to 110° to 130°C (230° to 266°F) and press service valve guide into cylinder head at specified height.
Projection "L": 11.5 - 11.7 mm (0.453 - 0.461 inch)





5. Ream the new valve guide to the specified inner diameter.
Inner diameter finished size
Intake & Exhaust: 5.500 - 5.515 mm (0.2165 - 0.2171 inch)

VALVE SEATS





Check valve seats for pitting at contact surface. Resurface or replace if excessively worn.

NOTE:
- 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. Set machine depth stop so that boring cannot contact the bottom face of seat recess in cylinder head.
2. Ream cylinder head recess.

NOTE: Use the valve guide center for reaming to ensure valve seat will have the correct fit.





3. Heat cylinder head to 110° to 130°C (230° to 266°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: 1.06 - 1.34 mm (0.0417 - 0.0528 inch)
Exhaust: 1.34 - 1.63 mm (0.0528 - 0.0642 inch)





8. Use a depth gauge to measure the distance "L" 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 correct it. If the distance is longer, replace the valve seat.
Valve seat resurface limit
Intake: 35.95 - 36.55 mm (1.4154 - 1.4390 inch)
Exhaust: 35.92 - 36.52 mm (1.4142 - 1.4378 inch)

VALVE DIMENSIONS
Check dimensions of each valve.

VALVE SPRING
Squareness





1. Measure dimension "S".
Out-of-square "S": Less than 1.75 mm (0.0689 inch)
2. If it exceeds the limit, replace the spring.

Pressure





Check valve spring pressure at specified spring height.
Valve spring pressure
Standard: 370.0 N (37.73 kg, 83.19 lb) at 23.64 mm (0.9307 inch)
Limit: More than 347.8 N (35.46 kg, 78.19 lb) at 23.64 mm (0.9307 inch)
If not within specification, replace the spring.

Cylinder Head:

Cylinder Head