SECTION 4. DISASSEMBLY AND SERVICE
d) Check the valve stem-to-guide clearance.
e) Valve stem-to-guide clearance: Deduct the valve stem
outside diameter from the valve guide bore’s inside diameter
to get the clearance between the valve guide and valve stem.
f) If the clearance is over the service limit, judge whether a
new guide can make the clearance within service limit,
if it
can, replace the guide and ream the guide, recondition the
valve seat when replacing the valve guide.
5) VALVE SEAT:
a) Thoroughly clean the combustion chamber and valve seats
to remove carbon deposits.
Apply a light coat of red lead
powder or erasable color painting to the valve faces.
b) Insert the valves, and then press the valve several times
forcefully
.
Be sure the valve does not rotate on the seat.
The transferred marking compound will show any area
of the seat that is not concentric with the valve.
c) Using a 45°cutter, remove enough material to produce a
smooth and concentric seat. Turn the cutter clockwise, never
counterclockwise. Continue to turn the cutter as you lift it
from the valve seat.
Tool: Valve seat cutter
d) Use the 32°-45°cutters to narrow and adjust the valve seat
so that it contacts the middle of the valve face.
The 32°cutter removes material from the top edge (contact
too high).
The 45°cutter removes material from the bottom edge
(contact too low). Be sure that the width of the finished
valve seat is within specification.
Standard
Service limit
0.8 mm
2.0 mm
VALVE
GUIDE
CLIP
VALVE
GUIDE
DRIVER
VALVE
GUIDE
INSTALLATI
ON HEIGHT
1mm
VALVE
SEAT
CUTTER
VALVE
FACE
IN: 32°
EX: 32°
IN: 45°
EX: 45°
CONTACT
TOO HIGH
CONTACT
TOO LOW
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