Valve guides and valve sea ts
(1) Check each valve for carboning, burning, wear or
other defect on head; also check cap end and stem
for cracks. Replace the valve if damaged.
(2)
Check each valve guide for wear. Remember, the
guide wears down more rapidly at its both ends
than at any other parts. Measure the inside dia·
meter of the guide at its ends and at its middle
part in two directions. Measure the outside dia·
meter of each valve stem. If the measurement
exceeds the repair limit in Table below, replace
the valve guide.
(3) Valve face and valve seat
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Wear on valve guide
Specifications
Unit: mm (in.)
Check valve face and valve seat for wear and
contact. If valve face is found excessively worn,
reface it by using a valve refacer. To reface the
valve, proceed as follows:
Item
Standard
Repair
limit
Clearance
of valve
stem in
valve guide
Valve guide
length out-
side hole
Valve stem
diameter
Specifications
Item
Nominal
Standard
Repair
value
limit
Angle
30
°
Sinkage
±0.2
13
Valve
0.8 (0.031)
(±0.008}
(0.051)
seat
Width
1.4 (0.055)
±0.14
1.6
(±0.0055)
(0.063)
Reface up to
Valve margin
1.7 (0.067)
1.2
(0.047)
Intake
Exhaust
Intake
Exhaust
0.055-0.085
{0.00217-0.00335}
0.070-0.105
(0.00276-0.00413)
18
±
0.3
(0.709 ± 0.012)
g -0.045
-0.060
(0 315 -0.00177}
·
-0.00236
g-0.060
-0.080
(0315-0.00236)
-0.00315
0.15
(0.0059)
0.20
(0.0079)
-0.10
(-0.0039)
-0.15
(-0.0059)
Unit: mm (in.)
Service limit
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5 i- Bore diam
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Face•
Valve seet
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i
angle
j Counterbore Valve margin
