Yanmar 4LHA-HTP User Manual

Chapter 2 Basic Engine
4. Cylinder Head
t
4LHA Series
(1) Rocker arm shaft and rocker arm bushing
Measure the outer diameter of the shaft and the inner
diameter of the bushing, and replace if wear exceeds the
limit.
mm(in.)
Standard
Wear limit
Intake and exhaust
valve rocker arm
shaft outside dia.
18.459-18.479
(0.7267 - 0.7275)
18.35
(0.7224)
Intake and exhaust
valve rocker arm bush-
ing inside dia.(assembled)
18.50-18.52
(0.7283 - 0.7291)
18.60
(0.7323)
Valve rocker arm shaft
and bushing clearance
at assembly
0.021 - 0.061
(0.0008 - 0.0024)
Replace the rocker arm shaft bushing if it moves and replace
the entire rocker arm if there is no tightening shrinkage.
(2) Rocker arm spring
Check the rocker arm spring and replace it if it is corroded
or wom.
(3) Rocker arm and valve top cap wear
Inspect the contact surface of the rocker arm and replace it
if there is abnormal wear of flaking.
(4) Inspect the contact surface of the valve clearance
adjustment screw and push rod and replace if there is
abnormal wear or flaking.
4-8 Adjustment of valve clearance
(1) Make adjustments when the engine is cool.
4LHA-STE/-STZE
4LHA-STP/-STZP
4LHA-DTE/-DI Zh
4LHA-DTP/-DTZP
4LHA-HTE/-HTZE
4LHA-HTP/-HTZP
Intake
0.1
0.1
0.1
Exhaust
0.5
0.4
0.3
Adjusting
screw
Lock nut
(2) Be sure to adjust the opening and closing angles for
both the'intake and exhaust valves when reassem-
bling the timing gear.
T.D.C.
b.TDC
a.TDC
b.BDC
a.BDC
B.DC.
Deg.
4LHA-HTE/
-HTZE
-HTP/
-HTZP
4LHA
-STE/STZE
-STP/STZP
-DTE/DTZE
-DTP/DTZP
Intake valve open
b.TDC
59±5
-
59±5
Intake valve closed
a.BDC
63±5
-
63±5
Exhaust valve open
b.BDC
51 ±5"
58±5
Exhaust valve closed
a.TDC
39±5-
46±5
2-20

Yanmar 4LHA-HTP Specifications

General

Brand	Yanmar
Model	4LHA-HTP
Category	Engine
Language	English