1D-39 Power Unit Mechanical:
Valve seat servicing
If valve seat contact width is out of specification, reface
valve seat as follows:
Valve seat angle
Intake side: 30° / 45° / 60°
Exhaust side: 15° / 45°
To reface a valve seat, use the following valve seat
cutting tool.
• Valve seat cutter 45° (Neway 122)
• Valve seat cutter 30° (Neway 126)
• Valve seat cutter 15° (Neway 120)
• Valve seat cutter 60° (Neway 111)
• Solid pilot (Neway, N-100-5.52) (09916-24450)
• Handle (Neway, N-505) (09916-54910)
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 “a”.
Refer to “Valve seat contact width” (Page 1D-38).
Too high (wide)
Too low (narrow)
• If width “a” is too high (or wide), reface valve seat
using small angle cutter (Intake side: 30°, Exhaust
side: 15°).
• If width “a” is too low (or narrow), reface valve seat
using 60° angle cutter (Intake side).
• If width “a” is too low (or narrow), reface valve seat
using 45° angle cutter (Exhaust side).
4) Clean up any burrs using 45° angle cutter very
lightly.
CAUTION
Cut seat areas minimally only.
Do not cut more than necessary.
5) Lap valve on seat in two steps, first with coarse grit
lapping compound applied to face and the second
with fine grit compound.
6) Recheck valve seat contact width “a”.
NOTE
Clean and assemble cylinder head and valve
components.
Fill intake and exhaust ports with solvent to
check for leaks between valve seat and valve.
If any leaks occur, inspect valve seat and
face for burrs or other things that could
prevent valve from sealing.
IN. EX.
30°
45°
60°
15°
45°
I9J011140046-02
“a”
I9J011140047-01
“a”
I9J011140048-01
I9J011140049-01
I9J011140220-01
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