Valve: Service and Repair
Valve and Valve Guide1. Inspect each valve for the following. Replace or resurface it necessary.
(1) Damaged or bent stem
(2) Roughness or damage to face
(3) Damage or uneven wear of stem tip
2. Check the valve head margin thickness. Replace if necessary
Margin thickness:
IN : 0.5mm (0.020 in) min.
EX : 1.0mm (0.039 in) min.
3. Measure the valve length.
Length:
IN : 115.81mm (4.5594 in)
EX : 116.2lmm (4.5752 in)
4. Measure the valve stem diameter.
Diameter:
IN: 6.970-6.985mm (0.2744-0.2750 in)
EX: 6.965-6.980mm (0.2742-0.2748 in)
5. Measure the valve guide inner diameter.
Inner diameter:
IN: 7.01-7.O3mm (0.2760-0.2768 in)
EX: 7.01-7.03mm (0.2760-0.2768 in)
6. Measure the valve stem to guide clearance.
(1) Method No.1
Subtract the outer diameter of the valve stem from the inner diameter of the corresponding valve guide.
(2) Method No.2
Measure the valve stem play at a point close to the valve guide with the valve lifted slightly off the valve seat.
Clearance:
IN: 0.025-0.0B0mm (0.0010-0.0024 in)
EX: 0.030-0.065mm (0.0012-0.0026 in)
Maximum: 0.20mm (0.0079 in)
7. It the clearance exceeds specification, replace the valve and/or valve guide.
8. Check that the valve guide protrusion height (dimension A in the image). Replace if necessary.
Height: 19.8-20.3mm (0.780-0.799 in)
Replacement of valve guide
Note
^ Although the shapes of the intake and exhaust valve guides are different, use the exhaust valve guide on both sides as a replacement.
Removal
Remove the valve guide from the side opposite the combustion chamber with the SST.
Installation
1. Assemble the SST so that the depth L is as specified.
Depth L: 19.8-20.3mm (0.780-0.799 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. Check that the valve guide projection height is within specification.
5. If not within specification, repeat steps 1-4.
Valve Seat
1. Inspect the contact surface of the 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 rotating the valve against the seat.
(1) It 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. Check the seat contact width.
Width: 1.2-1.6mm (0.047-0.063 in)
6. Check 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 with a 60° cutter and a 45° cutter.
(2) If the seating position is too low, correct the valve seat with a 35° (IN) or 15° (EX) cutter and a 45° cutter.
7. Seat the valve to the valve seat with a lapping compound.
8. Check the sinking of the valve seat. Measure protruding length (dimension L) of each valve stem.
Dimension L: 50.2mm (1.976 in)
(1) It L is as below, it can be used as it is.
50.2-51.0mm (1.976-2.008 in)
(2) If L is as below, insert a spacer between the spring seat and cylinder head to adjust.
51.0-51.7mm (2.008-2.035 in)
(3) If L is more than as below, replace the cylinder head.
51.7mm (2.035 in) or more
Valve Spring
1. Inspect each valve spring for cracks or damage.
2. Check the free length and angle. Replace if necessary.
Free length:
IN Standard: 49.5mm (1.949 in) Minimum: 48.3mm (1.902 in)
EX Standard: 50.4mm (1.984 in) Minimum: 49.2mm (1.937 in)
Angle: 1.7mm (0.067 in) max.