Yanmar 4LHA-HTP Operation Manual page 338

Chapter 2 Basic Engine
4. Cylinder Head
(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.
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
Valve stem seal
Valve guide
^ C y l i n d e r head
(4) Measure spring tension.
Measure the spring
force at
• Outer spring height
Kl : 37.5mm
K2 :26.5mm
• Inner spring height
K1 :37.75mm
K2 : 24.75mm
Valve spring
Free length Free length mm mm
mm
Inclination
N N
Spring force Spring force
(kgf) (kgf)
Assembling valve springs.
The side with the smaller pitch (painted white) should face
down (cylinder head).
Up side
Down side
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
i4LHA Series
Spring tension tester
Wear limit
Standard
45.15 (outer) 44.65
44.65
44.75 (inner)
1.2
^ Æ l (inner)
7
19.09(K2) '
V
n
CC
33
CC
J D
CT
r r
—Painted (white)