3.20
ENGINE
3. Place 46ï‚° cutter on the pilot and make a light cut.
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
ï‚° 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 and
must be replaced. Be sure the cylinder head is at the
proper temperature and replace the guide.
• 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 Blueâ„¢ paste to the valve seat. If
using an interference angle (46
ï‚°)apply black 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 Blueâ„¢ or
black marker 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 (A).
• 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
ï‚° cutter to lower the valve
seat.
• If too low use the 60
ï‚°or 75ï‚° 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
ï‚° cutter and
re-check contact point on the valve face and seat width
after each cut.
Proper Seat Contact On Valve Face
(A)
(B)
Bottom 60
o
or 75
o
Top 30
o
Seat 45
o
or 46
o
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