Sym Wolf SB 250 Ni Service Manual page 126

7. Cylinder Head / Valve
Use the 60 degree cutter to remove the
bottom 1/4 part of the seat and check the new
valve seat.
Use the 45 degree cutter to cut the seat to the
proper width.
Caution
Confirm that all roughness is removed.
●
Re-grind if necessary.
Coat the valve seat surface with Prussian blue
or red lead.
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 surface 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 surface 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.
7-12
Contact surface
too high
Contact surface
too low
Old valve
seat width
60°
1.0mm
45°
Old valve
seat width
32°
Old valve
seat width
60°