Suzuki DF 40 Service Manual page 177

VALVE SEAT SERVICING
If valve seat contact width is out of specification, reface valve
seat as follows :
• Valve seat angle
Intake side : 30° ° ° ° ° , 45° ° ° ° °
Exhaust side : 15° ° ° ° ° , 45° ° ° ° °
09916-20620 : Valve seat cutter (NEWAY122) 45° ° ° ° °
09916-20610 : Valve seat cutter (NEWAY121) 15° ° ° ° °
09916-20630 : Valve seat cutter (NEWAY 126) 30° ° ° ° °
09916-24440 : Handle adaptor (N-503-1)
09916-24450 : Solid pilot (N-100-5.52)
09916-24980 : Handle (N-503)
NOTE:
Turn cutter clockwise, never counterclockwise.
(1) Remove all carbon from valve and valve seat.
(2) Using 45° angle cutter, reface valve seat.
(3) Check valve seat contact width
See the "Valve seat contact width" section on page 6-33.
(4) If width is too high (or wide), reface valve seat using small
angle cutter (Intake side : 30° , Exhaust side : 15° ).
If width is too low (or narrow), reface valve seat using
45° angle cutter.
(5) Clean up any burrs using 45° angle cutter very lightly.
Grind seat areas minimally only.
Do not grind more than necessary.
(6) Lap valve on seat in two steps, first with coarse grit lapping
compound applied to face and the second with fine grit
compound.
(7) Recheck valve seat contact width
.
.
POWER UNIT 6-34
IN
45°
30°
• Too high (wide)
• Too low (narrow)
EX
45°
15°