Value
Spring:
Check valve springs for cracks, worn
ends, distortion, and tension. If spring endsare worn,
check valve spring retainer for wear. Check for spring
distortion by placing spring on aflat surface next to a
square. Measure height of spring and rotate
it
against
square edge to measure distortion. If distortion
exceeds
0.06
inch
(1.5
mrn) replace spring. Check
spring tension at the installed height for both the
valve open and closed position using an accurate
valve spring tester. Replace any valve spring that is
weak, cracked, worn, or distorted.
Valve Rotators:
Positive type valve rotators prolong
valve life and decrease valve repairs. When func-
tioning properly, the valve is rotated a fraction of a
turn each time it opens. While at open position, the
valve must rotate freely. There is no easy way to
determine if a valve rotator is good or bad. Onan
recommends that valve rotators be replaced at each
major overhaul or
if
a build-up
of
carbon
is
noted on
valve face and valve seat.
Walve Seats:
Inspect valve seat inserts. If seats are
loose, cracked or severely pitted, new ones must be
installed. Remove valve seat inserts using a valve seat
removal tool. If valve seat insert bores in cylinder
block are damaged or worn
so
that a press fit cannot
be obtained when installing new standard size valve
seat inserts, the bores must be machined for an
oversize seat.
USE
NEW
VALVE SEAT
TO
ADJUST
PULLER
DEPTH
PULLER
JAWS
C-1104
FIGURE
4.
VALVE
SEAT
REMOVAL
Valve Seat Removal:
Remove carbon and combustion
deposits from valve seat. Select proper puller size
determined by inside diameter
of
valve seat. On some
pullers use a new seat as a guide to adjust puller depth
(Figure
4).
Puller jaws must expand into cylinder block
at the point where bottom of valve seat insert rests on
cylinder block (Figure
4).
Position puller on valve seat
and tighten hex nut. Clamp cylinder block to
a
solid
bench. Attach slide hammer to puller. Tighten hex nut
between each blow with the slide hammer.
*
VAL
L
CHECK THIS SURFACE
FOR
BURRS BEFORE
INSERTING SEAT
VT-1
ow
FIGURE
5.
INSERTING NEW VALVE SEAT
Valve Seat Installation:
After the old seat has been
removed, clean out any carbon or metal burrs from the
seat insert recess. Use a valve seat insert driver and
hammer to install the insert (Figure
5).
Drive the valve
seat insert in
so
that the insert enters the recess evenly.
Make certain that the valve seat insert rests solidly on
the bottom of the recess all the way around its
circumference.
*
Insert valve seat staker into valve seat or guide in
cylinder block. Using a lead hammer, strike the
staking tool asharp blow
to
wedge new valvesecurely
in place.
It
will
be
necessary to refinish valve seat
inserts before installing valves.
To
assure a tight valve seat fit and eliminate the
danger
of
seat loosening in the bore, valve seat must
be staked.
b
10-4
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