Overhaul

CYLINDER HEAD


Disassembly and Assembly












DISASSEMBLY
1. Remove spark plug using suitable tool.
2. Remove valve lifter.
- Identify installation positions, and store them without mixing them up.
3. Remove valve collet.





- Compress valve spring with Tool (A). Remove valve collet with a magnet tool (B).

CAUTION:
Be careful not to damage valve lifter holes.





4. Remove valve spring retainer and valve spring.
5. Push valve stem to combustion chamber side, and remove valve.
- Identify installation positions, and store them without mixing them up.





6. Remove valve oil seal using Tool (A).





7. Remove valve spring seat.
8. Remove valve seat, if necessary.
- 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.

CAUTION:
Never bore excessively to prevent cylinder head from scratching.
9. Remove valve guide, if necessary.





To remove valve guide, heat cylinder head to 110 to 130�C (230 a.
to 266�F) by soaking in heated oil (A).





b. Drive out valve guide with a press [under a 20 kN (2 ton, 2.2 US ton, 2.0 lmp ton) pressure] or a hammer and the valve guide drift.

WARNING:
Cylinder head contains heat. Wear protective equipment to avoid getting burned.

INSPECTION AFTER DISASSEMBLY

Valve Dimensions
- Check the dimensions of each valve. For the dimensions, Specifications.
- If dimensions are out of the standard, replace valve and check valve seat contact.

Valve Guide Clearance

Valve Stem Diameter





- Measure the diameter of valve stem with micrometer (A).

Standard : Specifications.

Valve Guide Inner Diameter
- Measure the inner diameter of valve guide with bore gauge.

Standard : Refer to Specifications.

Valve Guide Clearance
- (Valve guide clearance) = (Valve guide inner diameter) � (Valve stem diameter)

Standard : Specifications.

- If the calculated value exceeds the limit, replace valve and/or valve guide.

Valve Seat Contact





- After confirming that the dimensions of valve guides and valves are within the specifications, perform this procedure.
- Apply prussian blue (or white lead) onto contacting surface of valve seat to check the condition of the valve contact on the surface.
- Check if the contact area band is continuous all around the circumference.
- If not, grind to adjust valve fitting and check again. If the contacting surface still has "NG" conditions even after the re-check, replace valve seat. Overhaul.






Valve Spring Squareness





- Set a try square (A) along the side of valve spring and rotate spring. Measure the maximum clearance between the top of spring and try square.






- If it exceeds the limit, replace valve spring.

Valve Spring Dimensions and Valve Spring Pressure Load





- Check the valve spring pressure at specified spring height.

Standard : Specifications.

- If the installation load or load with valve open is out of the standard, replace valve spring.

Standard : Specifications.

ASSEMBLY
1. Install the valve guide, if necessary.

CAUTION:
Replace with oversize [0.2 mm (0.008 in)] valve guide.





a. Using suitable tool (A), ream cylinder head valve guide hole.

For service parts: Oversized [0.2 mm (0.008 in)] Specifications.





b. Heat cylinder head to 110 to 130�C (230 to 266�F) by soaking in heated oil (A).





c. Using suitable tool, press valve guide (1) from camshaft side to the dimensions as shown.

Projection H : Specifications.

WARNING:
Cylinder head (2) contains heat. Wear protective equipment to avoid getting burned.





d. Using suitable tool (A), apply reamer finish to valve guide.

Standard: Specifications.


2. Install the valve seat, if necessary.

CAUTION:
Replace with oversize [0.5 mm (0.020 in)] valve seat.





a. Ream cylinder head recess diameter (a) for service valve seat.

For service parts: Oversize [0.5 mm (0.020 in)] Specifications.

- Be sure to ream in circles concentric to valve guide center.
This will enable valve to fit correctly.





Heat cylinder head to 110 to 130�C (230 to 266�F) by soaking in b.
heated oil (A).
c. Use dry ice to thoroughly cool valve seats. Force fit valve seat into cylinder head.

WARNING:
- Cylinder head contains heat. Wear protective equipment to avoid getting burned.
- Avoid directly touching cold valve seats.





d. Using suitable tool or valve seat grinder, finish seat to the specified dimensions. Specifications.

CAUTION:
When using the valve seat cutter, firmly grip cutter handle with both hands. Then, press on the contacting surface all around the circumference to cut in a single drive. Improper pressure on with cutter or cutting many different times may result in stage valve seat.
e. Using compound, grind to adjust valve fitting.
f. Check again for normal contact. Overhaul.





3. Install valve oil seal.
- Install with Tool (A) to match dimension as shown.





4. Install valve spring seat.
5. Install valve.
- Install larger diameter to intake side.
6. Install valve spring.

NOTE:
It can be installed in either direction.
7. Install valve spring retainer.
8. Install valve collet.





- Compress valve spring with Tool (A). Install valve collet with a magnet hand (B).

CAUTION:
Be careful not to damage valve lifter holes.
- Tap valve stem edge lightly with a plastic hammer after installation to check its installed condition.





9. Install valve lifter.
10. Install spark plug with a suitable tool.