Yanmar 4LHA-HTP User Manual

Chapter 2 Basic Engine
4. Cylinder Head
,4LHA Serie.
4-3.2 Inspection of valve seat wear and contact surface
Inspect for valve seat scratches and excessive wear.
Check to make sure the contact surface is normal. The
seat angle must be checked and adjusted if the valve seat
contact surface is smaller than the width of the valve seat.
Note: Bear in mind that the intake and exhaust valves
have different diameters.
4-3.3 Valve sinking
Over long periods of use and repeated lappings, combus-
tion efficiency may drop. Measure the sinking distance
and replace the valve and valve seat if the valve sink ex-
ceeds the tolerance.
Sink
mm (in.)
Cylinder head
TT
7
Depth gauge
mm
Standard .
Wear limit
Valve sink
.4LHA-HTE/HTP
(Intake/Exhaust)
• 4LHA-STE/STP
DTE/DTP
(Exhaust)
0.2 - 0.4
1.8
Valve protrusion
4LHA-STE/STP
DTE/DTP
(Intake)
0.6 - 0.8
(Protrusion)
0.6 (sink)
4-3.4 Valve guide
(1) Measuring inner diameter of the valve guide.
Measure the inner diameter of the valve guide and
replace it if it exceeds the wear limit.
Standard Wear limit
Valve guide
inside dia.
Intake
9.00-9.015
(0.3543 - 0.3549)
9.1
(0.3583)
Valve guide
inside dia.
Exhaust
9.00-9.015
(0.3543 - 0.3549)
9.1
(0.3583)
NOTE: The inner diameter standard dimensions assume a
pressure fit.
(2) Replacing the valve guide
Use the insertion tool and tap in the guide with a
mallet.
The intake valve guide and exhaust valve guide are of
different shapes/dimensions. The one with a groove
around it is the exhaust valve guide and the one
without is the intake valve guide.
(3) Valve guide projection
The valve guide should protrusion 11.5 mm from the top of
the cylinder head .
7777
T
77
2-17

Yanmar 4LHA-HTP Specifications

General

Brand	Yanmar
Model	4LHA-HTP
Category	Engine
Language	English