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d. Af te r installing t h e valve guide, use 7mm
reamer (special to o l) t o obtain the proper valve
clearance.
Afte r fit tin g the valve guide i n t o th e cylinder
head, be sure
to
fo r m valve lapping. The valve must be replaced
w i t h a new one.
5. Grinding the valve seat
The valve seat is subject to severe wear similar
a.
t o valve face. Whenever the valve face i s re-
surfaced, the valve seat should also be re-sur
faced a t a 45° angle. I n addition, i f a new valve
guide has been installed ( w i t h o u t any valve re-
pair), the valve seat should be checked to
guarantee complete sealing between the valve
face and seat.
CAUTION:
I f th e valve seat is obviously
pitted or worn, it should be cleaned w i t h a
valve seat cutter. Use the 45° cutter, and when
twisting th e cutter, keep an even downward
pressure to prevent chatter marks.
If cuttin g section " A ' o f the intake valve seat,
use " F L A T " cutter (radius cutter). If cuttin g
section "A" o f the exhaust valve seat, use
" F L A T " cutter (also: radiused). If c ut tin g sec-
tion "B", use the 4 5 °cutter.
b. Measure valve seat width. A p p ly mechanic's
bluing dye (such as Dyke m) to the valve face,
apply a very small amount of fine grinding
compound around the surface o f the valve
seat, insert the valve i n t o position, and spin the
valve q u ick ly back and forth. Li ft th e valve,
clean o f f all grinding compound, and check
valve seat width. The valve seat w i ll have re-
moved the bluing wherever it contacted the
valve face. Measure the seat w i d t h w i t h vernier
calipers.
It should measure approximately
(.05").
1.3mm
Also, the se at should be un iform
If valve seat w i d t h varies,
in contact area.
grind the valve seat, and per-
s t il l exist, then continue to c u t w i t h the
pits
45° cutter. Remove just enough material t o
achieve a satisfactory seat.
Seat w id th
c. If the valve seat is uniform around the perim-
eter of the valve face, b u t i s t o o wide or not
centered o n the valve face, it must be altered.
Use either the " FLAT" , 4 5 °or
t o correct the improper seat location in the
manner described below:
1) I f the valve face shows that the valve seat is
centered o n th e valve face, but t o o wide,
then lig htly use both the " F L A T " and th e
30° cutters t o reduce the seat w i d t h to
1.3mm (.05").
If the seat shows
2)
valve face, but too narrow, use the 4 5 °
cutter u n t il the w i d t h equals 1.3mm (.05").
If the seat i s t o o narrow and rig ht u p near
3)
the valve margin, then first use th e" F LA T"
cutter and then the 45° cutter to get the
correct seat width.
4) If the seat is too narrow and d o w n near the
bottom edge o f the valve face, then fir st use
the 30° cutter and then the 45° cutter.
I
6.
Lapping th e valve/valve seat assembly
a. The valve/valve seat assembly should be lapped
if (1) neither the seat no r the valve face are
severely worn, or
or if
Wear Limit
Standard Width
1.3mm
(.050")
to be in the mid dle o f t h e
(2)
if th e valve face and valve
2.0mm
(.080)
30°
cutters
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