Service Manual
Valve Spring:
Check valve springs for cracks, worn
ends, distortion, and tension.
If
spring ends are worn,
check valve spring retainer for wear. Check for spring
distortion by placing spring on a flat 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 mm) 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:
The P216, P218, and P220 engines use
free-rotating intake and exhaust valves. while in the
open position, the valves must rotate freely.
The P224 engine uses positive
type
valve rotators on the
exhaust valves. When functioning properly, the valves
are rotated a fraction of a turn each time they open.
While in the
open
position, the valves 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.
Valve
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
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. 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.
VALVE
VALVE
SEAT
INSERT
DRIVER
(USE
PROPER
TOOL)
K
THIS
SURFACE
BURRS
BEFORE
INSERTING
SEAT
FIGURE
5.
INSERTING
NEW
VALVE
SEAT
Valve
Seat
Installatlon:
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
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.
To assure a tight valve seat fit and eliminate the danger
of seat loosening in the bore, valve seat must be staked.
Insert valve: seat staker into valve seat
,or
guide in
tool a sharp blow to wedge new valve seat securely in
place. It
will
be necessary to refinish valve seat inserts
PULLER
JAWS
cylinder block. Using a lead hammer, strike the staking
FIGURE
4.
VALVE
SEAT
REMOVAL
before installing valves.
10-4