Honda XL125LK, Owner'S Manual

Page: 109 / 243

8-16
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CYLINDER HEAD/VALVES
The valve cannot
be grounded. If the
valve face is burned
or badly worn or if it
contacts the seat
unevenly, replace
the valve.
Remove the valve and inspect the width of each valve
seat.
The valve seat contact should be within the specified
width and even all around the circumference.
If the valve seat width is not within specification, reface
the valve seat.
Inspect the valve seat face for:
• Damaged face:
– Replace the valve and reface the valve seat.
• Uneven seat width:
– Bent or collapsed valve stem;
Replace the valve and reface the valve seat.
• Contact area (too high or too low area)
– Reface the valve seat.
VALVE SEAT REFACING
Follow the refacing
manufacturer’s
operating
instructions.
Valve Seat Cutters, a grinder or equivalent valve seat
refacing equipment are recommended to correct a worn
valve seat.
Using 45 degree cutter and cut the seat to the proper
width.
Make sure that all pitting and irregularities are removed.
Refinish if necessary.
After cutting the seat, apply lapping compound to the
valve face and lap the valve using light pressure.
Change the angle of lapping tool [1] frequently to
prevent uneven seat wear.
After lapping, wash any residual compound off the
cylinder head and valve.
Recheck the seat contact after lapping.
STANDARD: 0.9 – 1.1 mm (0.035 – 0.043 in)
SERVICE LIMIT: 1.5 mm (0.06 in)
SEAT WIDTH
TOOLS:
Seat cutter, 27.5 mm (45° IN)
07780-0010200
Seat cutter, 24.5 mm (45° EX) 07780-0010100
Flat cutter, 28 mm (32° IN) 07780-0012100
Flat cutter, 25 mm (32° EX) 07780-0012000
Interior cutter, 30 mm (60° IN) 07780-0014000
Interior cutter, 22 mm (60° EX) 07780-0014202
Cutter holder 07781-0010400
STANDARD SEAT WIDTH:
0.9 – 1.1 mm (0.035 – 0.043 in)
Excessive lapping
pressure may
deform or damage
the seat.
Lapping compound
can cause damage
if it enters between
the valve stem and
guide.
32°
45°
60°
[1]