Yanmar 4LHA-STP User Manual

Chapter 2 Basic Engine
4. Cylinder Head
i4LHA Series
(4) Valve stem seals
The valve stem seals in the intake/exhaust valve guides
cannot be re-used once they are removed—be sure to
replace them.
When assembling the intake/exhaust valves, apply an
adequate amount of engine oil on the valve stem
before inserting them.
(4) Measure spring tension.
Valve stem seal
Valve guide
^Cylinder head
7^
4-4 Valve springs
4-4.1 Checking valve springs
(1) Check the spring for scratches or corrosion.
(2) Measure the free length of the spring.
(3) Measure inclination.
Square gauge
Measure the spring
force at
• Outer spring height
Kl : 37.5mm
K2 :26.5mm
• Inner spring height
K1 :37.75mm
K2 : 24.75mm
Spring tension tester
Valve spring
Standard
Wear limit
Free length
mm
45.15 (outer)
44.65
Free length
mm
44.75 (inner)
44.65
Inclination
mm
1.2
Spring force
N
(kgf)
Spring force
N
(kgf)
7
^
n
Æl (inner)
19.09(K2)
V
'
Assembling valve springs.
The side with the smaller pitch (painted white) should face
down (cylinder head).
Up side
CC
CC
33
Down side
CT
JD
rr
—Painted (white)
NOTE : The pitch of the valve spring is not even. The side
with the smaller pitch (painted white) should face
down (cylinder head) when assembled.
(5) Spring retainer and spring cotter
Inspect the inside face of the spring retainer, the
outside surface of the spring cotter, the contact area of
the spring cotter inside surface and the notch in the
head of the valve stem. Replace the spring retainer and
spring cotter when the contact area is less than 70%, or
when the spring cotter has been recessed because of
wear.
2-18

Yanmar 4LHA-STP Specifications

General

Number of Cylinders	4
Fuel System	Direct Injection
Engine Type	4-Stroke Vertical Water-Cooled Diesel Engine
Displacement	3.455 L
Bore x Stroke	100 mm x 110 mm
Aspiration	Turbocharged