Sym JOYRIDE 125 - Page 137

7. Cylinder Head / Valve
7-10
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
Grind valve seat again if necessary.
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
If the contact surface too high, grind the valve
seat with 32° cutter.
Then, grind the valve seat to specified width.
If the contact surface too low, grind the valve
seat with 60° cutter.
Then, grind the valve seat to specified width.
z Make sure that all roughness and uneven
faces had been ground.
z The contact surfaces of valve and valve
seat are very important to the valve
sealing capacity.
Old valve seat width
60°
45°
1.0mm (0.04 in)
Contact surface too
high
Contact surface too
low
32°
60°
Old valve seat width
Old valve seat width
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