Sym GTS 250, Service Manual

Page: 82 / 217

6. Cylinder Head / Valve
6-11
Valve Seat Inspection and Service
Clean up all carbon deposits onto intake and
exhaust valves.
Apply with emery slightly onto valve contact face.
Grind valve seat with a rubber hose or other
manual grinding tool.
Caution
y
Do not let emery enter into between valve stem
and valve guide.
y
Clean up the emery after corrected, and apply
with engine oil onto contact faces of valve and
valve seat.
Remove the valve and check its contact face.
Caution
Replace the valve with new one if valve seal is
roughness, wear out, or incomplete contacted
with valve seat.
Valve seat inspection
If the valve seat is too width, narrow or rough,
corrects it.
Valve seat width
Service limit: 1.6mm
Check the contact condition of valve seat.
Valve seat grinding
The worn valve seat has to be ground with valve
seat chamfer cutter.
Refer to operation manual of the valve seat
chamfer cutter.
Use 45° valve seat chamfer cutter to cut any rough
or uneven surface from valve seat.
Caution
After valve guide had been replaced, it has to be
ground with 45° valve seal chamfer cutter to
correct its seat face.
Use 32° cutter to cut a quarter upper parts out.
45°
Roughness
Old valve seat width
Valve seat width
32°
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