Doosan DX60R Shop Manual page 296

Valve Face and Valve Seat
Always check the clearance between the valve and valve guide
before grinding or lapping the valve seats. See "Intake /
Exhaust Valve and Guide" on page -95 for the service limit. If
the clearance exceeds the limit, replace the valve and/or valve
guide to bring the clearance within the limit.
Roughness or burrs will cause poor seating of a valve. Visually
inspect the seating surfaces of each valve and valve seat to
determine if lapping or grinding is needed.
Visually inspect all valves faces and valve seats for pitting,
distortion, cracking, or evidence of overheating. Usually the
valves and valve seats can be lapped or ground to return them
to serviceable condition.
components will require replacement.
Coat the valve seat with a thin coat of bluing compound. Install
the valve and rotate to distribute bluing onto the valve face. The
contact pattern should be approximately centered on the valve
face (1, Figure 143) and even in width.
Also visually inspect the valve seat for even contact.
Light cutting can be performed by the use of a hand-operated
cutter (Figure 144).
Valve seat diameter can be adjusted by top-grinding with a
150° stone to make the seat diameter smaller, and bottom-
grinding using a 40° stone to make the seat diameter larger.
Once the seat location has been corrected, grind and lap the
seat angle (1, Figure 144) to specification. See "Cylinder Head"
on page -95 for specifications.
Grind the valve face and/or valve seat as necessary to return
them to serviceable condition. Grinding is needed if the valve
and valve seat do not contact correctly. Check the valve margin
and valve recession after grinding.
If the valve or seat require grinding, lap the valve after grinding.
Lap the valve face to the valve seat using a mixture of valve
lapping compound and engine oil.
Be sure to thoroughly wash all parts to remove all grinding
powder or compound.
Inspection of Valve Springs
Inspect the valve springs. If damage or corrosion is seen, or if
measurements exceed the specified limits, replace the springs.
Fractures
Check for fractures on the inside and outside portions of the
springs. If the valve spring is fractured, replace the valve
spring.
Corrosion
Check for corrosion of spring material caused by oxidation.
Engine
Page 116
Severely worn or
Figure 143
damaged
Figure 144
1
FG008890
SP001693