SANYANG INDUSTRY CO. SYM Service Manual page 72

SYM
Valve seat inspection
If the valve seat is too width, narrow or rough,
correct 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 grinded with
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 grinded with 45° valve seal chamfer
cutter to correct its seat face.
Use 32° cutter to cut a quarter upper part
out.
Use 60° cutter to cut a quarter lower part out.
Remove the cutter and check new valve
seat.
Use 45° cutter to grind the valve seat to
specified width.
Caution
Make sure that all roughness and uneven
faces had been grinded.
Grind valve seat again if necessary.
6. CYLINDER HEAD/VALVE
Roughness
45°
Old valve seat width
Old valve seat width
1.0mm
32°
60°
45°
6-11