Sym MB10A7-A series Service Manual page 113

7. Cylinder Head / Valve
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Valve Seat Inspection / Refacing
Inspection
Clean up all carbon deposits on the intake and
exhaust valve seats.
Apply some red lead paint onto valve contact
face.
Grind valve seat with a rubber hose or other
manual grinding tool.
Remove the valve and check if the contact
face is even.
Caution
The valve can not be ground. If the valve
is burned, worn, or its contact face is
uneven, replace it.
If the valve contacts the seat unevenly
after grinding, replace it.
Check the valve seat contact condition.
If the valve seat is too wide, narrow or rough,
corrects it.
Service limit：Valve seat width
Valve contact face 1.8 mm
Valve seat refacing
The worn valve seat has to be ground with
valve seat cutter/ grinder.
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1.6 mm
Service limit：1.6mm
Valve seat width
Service limit：1.8mm
60∘
32∘
45∘