6-24 POWER UNIT
VALVE SEAT SERVICING
If the valve seating contact width is out of the specification, reface
the valve seat as follows:
$
09916-24940: Solid pilot (N-150-7)
09916-54910: Handle (N-505)
09916-24935: Valve seat cutter (N-608)
09916-24910: Valve seat cutter (N-212)
NOTE:
Turn the cutter clockwise, never counterclockwise.
1. Insert the 45° cutter and reface the valve seat.
2. Measure the valve seating contact width
A
. See the “Valve
seating contact width” section on the page 6-23.
3. If the width
A
is too high (or wide), reface the valve seat
using the 15° cutter.
If the width
A
is too low (or narrow), reface the valve seat
using the 45° cutter.
4. Clean up any burrs using the 45° cutter very lightly.
15˚
45˚
60˚
IN
15˚
45˚
EX
Too high (wide)
Too low (narrow)
5. Refinish the valve guide bore.
$
09916-34520: Valve guide reamer (
φφφφφ
7 mm)
09916-34542: Valve guide reamer handle
NOTE:
Clean and oil the valve guide bore when reamed.
!
Do not use lapping compound after the final cut is
made. The finished valve seat should have a velvety
smooth finish and not a highly polished or shiny fin-
ish. This will provide a soft surface for the final seat-
ing of the valve which will occur during the first few
seconds of engine operation.
!
Grind the seat areas minimally only.
Do not grind more than necessary.
5. Recheck the valve seat contact width
A
.