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e) If the clearance is over the service limit, judge a new guide if it can make the clearance conforming to
service limit, if conforming to, replace the guide and ream the guide, refinish the valve when replacing the
valve guide.
④ Valve seat：
a) Thoroughly clean the combustion chambers 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 not to rotate valve on the seat.
Valve seat painted the color will show contacted with the valve. If not, the transferred marking compound
will show any area of the seat that is not concentric.
c) Using 45°cutter, remove enough material to produce a smooth and concentric seat. Turn cutter
clockwise, never counterclockwise.
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
0.8mm 2.0mm
Valve face
Cutter holder
IN valve：32°
EX valve：32°
IN valve：45°
EX valve：45°