Service Manual

3.30
ENGINE
4. Inspect the cut area of the seat:
* If the contact area is less than 75% of the circumference of the
seat, rotate the pilot 180
° and make another light cut.
* If the cutter now contacts the uncut portion of the seat, check
the pilot. Look for burrs, nicks, or runout. If the pilot is bent it
must be replaced.
* If the contact area of the cutter is in the same place, the valve
guide is distorted from improper installation
* If the contact area of the initial cut is greater than 75%,
continue to cut the seat until all pits are removed and a new seat
surface is evident. NOTE: Remove only the amount of material
necessary to repair the seat surface.
5. To check the contact area of the seat on the valve face, apply
a thin coating of Prussian Blue paste to the valve seat. If
using an interference angle (46
° ) apply black permanent
marker to the entire valve face (A).
6. Insert valve into guide and tap valve lightly into place a few
times.
7. Remove valve and check where the Prussian Blue

indicates seat contact on the valve face. The valve seat
should contact the middle of the valve face or slightly
above, and must be the proper width.
* If the indicated seat contact is at the top edge of the valve face
and contacts the margin area (B) it is too high on the valve face.
Use the 30
° cutter to lower the valve seat.
* If too low, use the 60
° cutter to raise the seat. When contact
area is centered on the valve face, measure seat width.
* If the seat is too wide or uneven, use both top and bottom
cutters to narrow the seat.
* If the seat is too narrow, widen using the 45
° cutter and re-
check contact point on the valve face and seat width after each
cut.
NOTE: When using an interference angle, the seat
contact point on the valve will be very narrow, and is
a normal condition. Look for an even and
continuous contact point all the way around the
valve face (A).
A
= In. / mm.
Valve Seat Width:
Intake Std: .028" (.7 mm)
Limit: .055" (1.4 mm)
Exhaust Std: .039I (1.0 mm)
Limit: .071" (1.8 mm)
B
A
Proper Seat Contact
on Valve Face
Bottom 60°
Seat 45°
Top 30°
Seat
Width