Yanmar 4JH4E - Page 86

2. Inspection and adjustment
66R1
3) Valve clearance adjustment - 4 valves system
a) Loosen adjusting bolts
The 4-valve cylinder head has a valve
bridge.
Remove the injector to make space for
inserting a wrench in order to hold valve
bridge.
IMPORTANT
Do not loosen or tighten the valve bridge
adjusting screw lock nut without holding
the valve bridge. Always hold the valve
bridge using a wrench to prevent bending
of the valve stems and/or valve bridge
guide.
• Loosen the bridge adjusting screw lock nut
while holding the bridge with a wrench.
• Loosen the adjusting screw by turning it 2
turns outside.
• Check for visible clearance between screw
and valve.
b) Adjust valve bridge clearance
[NOTICE]
• The valve bridge on the 4-valve system
enables one rocker arm to operate two
valves at the same time. Therefore the
valve bridge should be adjusted exactly
in horizontal position.
• The clearance between the valve bridge
and valves must be set before adjusting
the valve clearance (between rocker
arm and valve bridge).
• To assure the valve bridge has equal
contact with the front and rear valves, apply
light pressure (hold) by rocker arm (screw
in rocker arm adjusting screw until rocker
arm touches the valve bridge).
• Adjust the valve bridge adjusting screw, so
there is zero “0” clearance between the
adjustment screw and the front valve.
• Tighten the locknut, while holding the valve
bridge with a wrench. Verify that the valve
bridge clearance is zero “0”.
c) Valve clearance adjustment
• Insert a 0.2 mm thickness feeler gauge
between the rocker arm and valve bridge.
• Adjust the valve clearance by turning the
adjustment screw until there is a slight
“drag” on the feeler gauge when sliding it
between the rocker arm and the valve
bridge.
• Tighten the lock nut.
• Apply oil to the contact surface between
adjusting screw and push rod.
Standard intake/exhaust valve clearance (mm)
0.15-0.25
Adjusting
screw
Loosen
Loosen
Wrench
Valve
bridge
010431-01E
4 valve cylinder head
Adjusting
screw
Tighten
Tighten
Wrench
Valve
bridge
010430-01E
Valve clearance
Clearance 0
Rocker arm adjusting screw
Rocker arm
Lock nut
Valve bridge
adjusting screw
A
djusting valve
bridge clearance
to 0
Lock nut
Valve bridge
017866-00E
Valve clearance
Rocker arm adjusting screw
017879-00E