Yanmar 4LHA-HTP Operation Manual page 336

Chapter 2 Basic Engine
4. Cylinder Head
4-2 Valve seat correction procedure
The most common method for correcting unevenness of
the seat surface with a seat grinder is as foflows :
(1) Use a seat grinder to make the surface even.
First use a TO" (for STE/DTE/STP/DTP exhaust and
HTE/HTP intake), 80'(for STE/STP/DTE/DTP intake
and HTE/HTP exhaust) grinder, then grind the seat to the
standard dimension (45*for exhaust), (30°for intake)
using the seat grinder with 15'chanfer.
Intake valve
Seat grinder
(standard angle)
Exhaust valve
NOTE : When seat adjustment is necessary, be sure to
check the valve and valve guide. If the clearance
exceeds the tolerance, replace the valve or the valve
guide, and then grind the seat.
Seat width
Exhaust valve seat
(2) Knead oil into the valve compound and finish the
valve seat using a lapping tool.
(3) Final finishing should
be done with oil only.
Lapping tool
Use a rubber cap type lapping
tool for valves without
a lapping tool groove slit.
at grinder
4-3 Intake/exchaust valves, valve guides
4-3.1 Wearing and corrosion of valve stem
30'
45"
corroded.
Seat width
Intake valve seat
2-16
NOTE : Clean the valve and cylinder head with diesel fuel
oil after valve seat finishing is completed, and make
sure that there are no grindings remaining.
NOTE: 1. Insert adjusting shims between the valve spring
and cylinder head when seats have been re-
finished with a seat grinder.
2. Measure valve distortion
finishing has been completed, and replace the
valve and valve seat if it exceeds the tolerance.
Replace the valve if the valve stem is excessively worn or
K L
r
40 mm
(1.57)
Valve stem
Standard
outside dia.
8.96 - 8.975
Intake
(0.3528 - 0.3533)
8.94 - 8.955
Exhaust
(0 352 - 0.3526)
i4LHA Series
Lapping tool
after valve seat re-
ffl-
60 mm
(2.36)
mm (in.)
Wear limit
8.9 (0.3504)
8.9 (0.3504)