Valve: Service and Repair

VALVE MECHANISM

Valve and Valve Guide
1. Inspect each valve for the following. Replace or resurface the valves as necessary.
(1) Damaged or bent stem
(2) Rough or damaged face
(3) Damaged or unevenly worn stem tip

2. Measure the head margin thickness of each valve Replace the valves if necessary.

Margin thickness
IN :1.10 mm (0.0433 in)
EX :1.20 mm (0.0472 in)





3. Measure the length of each valve and replace the valves if necessary.

Length
Standard
IN : 89.68 mm (3.5307 in)
EX : 89.78 mm (3.5346 in)
Minimum
IN : 89.28 mm (3.5150 in)
EX : 89.38 mm (3.5189 in)





4. Measure the diameter of each valve stem and replace the valves if necessary.

Diameter
Standard
IN : 5.970-5.985 mm (0.2351-0.2356 in)
EX : 5.965-5.980 mm (0.2340-0.2354 in)
Minimum
IN : 5.940 mm (0.2339 in)
EX : 5.935 mm (0.2337 in)





5. Measure the inner diameter of each valve guide at the points shown.

Inner diameter
IN : 6.01-6.03 mm (0.2367-0.2374 in)
EX : 6.01-6.03 mm (0.2367-0.2374 in)





6. Calculate the valve stem-to-guide clearance by subtracting the outer diameter of the valve stem from the inner diameter of the corresponding valve guide.

Clearance
IN : 0.025-0.060 mm (0.0010-0.0023 in)
EX : 0.030-0.065 mm (0.0012-0.0025 in)

Maximum: 0.10 mm (0.004 in)

7. If the clearance exceeds the maximum, replace the valve and/or the valve guide.





8. Measure each valve guide projection height (A). Replace the guides if necessary.

Height (A)
IN : 13.5-14.1 mm (0.532-0.555 in)
EX : 13.5-14.1 mm (0.532-0.555 in)





Replacement of valve guide

Note
^ The intake and exhaust valve guides are the same.





Removal
Remove the valve guide from the combustion chamber side by using the SST.





Installation
1. Assemble the SST so that depth L is as specified.
Depth L: 13.5-14.1 mm (0.532-0.555 in)

2. Tighten the locknut.





3. Tap the valve guide in from the side opposite the combustion chamber until the SST contacts the cylinder head.
4. Verify that the valve guide height is within the specification.
5. If not within the specification, repeat steps 1-4.





Valve Seat
1. Inspect the contact surface of each valve seat and valve face for the following:
(1) Roughness
(2) Damage

2. If necessary, resurface the valve seat with a 45 ° valve seat cutter and/or resurface the valve face.





3. Apply a thin coat of Prussian blue to the valve face.
4. Check the valve seating by pressing the valve against the seat.
(1) If blue does not appear 360 ° around the valve face, replace the valve.
(2) If blue does not appear 360 ° around the valve seat, resurface the seat.





5. Measure the seat contact width.
Width: 0.9-1.3 mm (0.036-0.051 in)





6. Verify that the valve seating position is at the center of the valve face.

(1) If the seating position is too high, correct the valve seat using 65 ° (IN) or 75 ° (EX) cutter, and a 45 ° cutter.
(2) If the seating position is too low, correct the valve seat using a 35 ° cutter and a 45 ° cutter.

7. Seat the valve to the valve seat by using a lapping compound.





8. Check the sinking of the valve seat. Measure the protruding length (dimension L) of the valve stem.

Dimension L: 39.0 mm (1.535 in)
(1) If L is 39.0-39.5 mm (1.536-1.555 in), no correction needed.
(2) If L is 40.6 mm (1.598 in) or more, replace cylinder head.








Valve Spring
1. Inspect each valve spring for cracks or damage.
2. Measure the free length and out-of-square. Replace the valve springs if necessary.

Free length
Standard: 44.0 mm (1.732 in)
Minimum: 36.5 mm (1.437 in)/177.1-200.2 Nm (18.05-20.42 kgf, 39.71-44.92 lbf)
Out-of-square: 1.54 mm (0.061 in) max.