1D-106 Engine Mechanical: For J20 Engine
Valve seat repair
A valve seat not producing a uniform contact with its
valve or showing width of seating contact that is out of
specified range must be repaired by regrinding or by
cutting and regrinding and finished by lapping.
1)
Exhaust valve seat:
Use valve seat cutters (1) to make two cuts as
illustrated in the figure. Two cutters must be used:
the first for making 15
°
angle, and the second for
making 45
°
angle. The second cut must be made to
produce desired seat width.
Seat width for exhaust valve seat
“a”: 1.0 – 1.4 mm (0.0389 – 0.0551 in.)
2)
Intake valve seat:
Use valve seat cutters (1) to make three cuts as
illustrated in the figure. Three cutters must be used:
the 1st for making 25
°
angle, the 2nd for making 60
°
angle, and 3rd for making 45
°
angle. The 3rd cut
(45
°
) must be made to produce desired seat width.
Seat width for intake valve seat
“b”: 1.0 – 1.4 mm (0.0389 – 0.0551 in.)
3)
Valve lapping:
Lap valve on seat in two steps, first with coarse size
lapping compound applied to face and the second
with fine-size compound, each time using valve
lapper according to usual lapping method.
Cylinder Head Inspection
S5JB0A1426047
• Remove all carbon deposits from combustion
chambers.
NOTE
Do not use any sharp-edged tool to scrape
off carbon deposits. Be careful not to scuff or
nick metal surfaces when decarbonizing. The
same applies to valves and valve seats, too.
• Check cylinder head for cracks on intake and exhaust
ports, combustion chambers, and head surface. Using
a straightedge and thickness gauge, check flatness of
gasketed surface at a total of 6 locations. If distortion
limit is exceeded, correct gasketed surface with a
surface plate and abrasive paper of about #400
(Waterproof silicon carbide abrasive paper): place
abrasive paper on and over surface plate, and rub
gasketed surface against paper to grind off high spots.
Should this fail to reduce thickness gauge readings to
within limit, replace cylinder head.
Leakage of combustion gases from this gasketed joint
is often due to warped gasketed surface: such
leakage results in reduced power output.
Distortion for cylinder head surface on piston side
Limit: 0.03 mm (0.001 in.)
I5JB0A142047-02
I2RH0B140105-01
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