Valve Seat and Valve Guide Replacement
Worn valve stem guides
or
valve seats that are loose,
cracked,
or
severely
pitted
should
be
replaced
by
replacing the cylinder head assembly. Both the valve
stem guides and the valve seats are available only as
part
of
the cylinder head assembly.
Valve
Lash
Adjustment
The engine is equipped with adjustable valve tappets.
Adjust the valve clearance when the engine is at
ambient temperature. Proceed as follows:
1.
2.
3.
4.
5.
6.
7.
Follow
head cover removal instructions (this sec-
tion). Inspect valve stems for proper alignment with
tappets.
Advance the engine until both
of
the valves are
closed and there is no pressure on the valve lifters
(piston at top dead center).
Clearances are shown in the Specifications section.
For each valve, the gauge should just pass between
the top of the valve stem and the rocker arm. (see
Figure
9-1
1).
Check the cylinder head mounting bolt torque (see
Cylinder Head, this section) before performing valve
lash adjustment.
To correct the valve clearance, place a
14
mm
wrench on the adjusting nut and a
10
mm wrench on
the outer locking nut. Loosen the outer locking nut
and turn the adjusting nut as needed
to
obtain the
correct clearance. Tighten locking nut after adjust-
ment is made.
Recheck the valve clearance after adjustment has
been made and also check the rocker arm bolts
to
see that they have not loosened asa result
of
adjust-
ing the valve lash.
Reinstall the head cover and torque head cover
bolts
to
specified torque.
CRANKCASE COVER
Remove the crankcase cover mounting
bolts
and lightly
tap
cover
with plastic
faced
hammer
to
loosen.
Be
care-
ful not
to
lose crankshaft and camshaft shims. When
installing the cover make sure the governor shaft is
properly positioned.
Use
a new gasket and clean the
crankcase cover and the engine block where the gasket
rests. Place crankcase cover in position and torque until
all bolts are tightened to the specified torque (see
Torque Specifications section).
C-1113
FIGURE 9-12. CRANKCASE COVER
CAMSHAFT AND TAPPET REMOVAL
The camshaft gear is pressed onto the camshaft and
should be removed from the engine as a set. Check for
matching mark with crankshaft before removing cam-
shaft. The tappets can be removed after camshaft
removal. See Figure
9-1
3.
TAPPETS
CAMSHAFT
GEAR
C-1114
FIGURE 9-11. VALVE
LASH
ADJUSTMENT
FIGURE 9-13. CAMSHAFT
AND
TAPPETS
9-5
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