Sym PA12B Service Manual page 110

Use the 45 degree cutter and cut the seat to
the proper width.
Caution
Confirm that all roughness is removed.
Coat the valve seat surface with red paint.
Install the valve through valve guide until the
valve contacting with valve seat, slightly press
down the valve but do not rotate it so that a
seal track will be created on contact surface.
Caution
The contact surfaces of valve and valve
seat are very important to the valve
sealing capacity.
If the contact face on the valve is too high, cut
the valve seat with the 32 degree cutter.
Then cut the valve seat to the proper width
with the 45 degree cutter.
If the contact face on the valve is too low, cut
the valve seat with the 60 degree cutter.
Then cut the valve seat to the proper width
with the 45 degree cutter.
After the valve seat ground, coat valve seat
surface with emery and then slightly press the
ground surface.
Clean up all emery coated onto cylinder and
valve after ground.
To this chapter contents
7. Cylinder Head / Valve
1.0mm
Contact face too
high
Contact face
too low
45°
Old valve seat
width
32°
Old valve seat
width
60°
7-13