Generac Power Systems OHVI GSH 220 Service Manual page 26

SeCTIoN 6: CYlINder HeAd ANd vAlveS
NOTE: Replace the cylinder head gasket every time the
cylinder head is removed. The new head gasket must be
free of nicks and scratches as these could cause leaks.
*
To prevent eye injury, always wear eye protection
when removing valve springs.
5. Place a commercially available small engine valve spring
compressor squarely on top of the valve spring retainer. The
split valve keepers should "pop" out (see Figure 6-5).
6. With the split valve spring keepers removed, remove the
valve spring retainers, valve springs, valve spring washers,
and the intake and exhaust valves.
7. Clean all parts. Remove carbon from the valve heads and
stems. Inspect the valves and valve seats. Service parts as
outlined under "Valve Service."
VALVE SPRING
RETAINER
SPLIT VALVE
KEEPERS
Figure 6-5. Remove Valve Spring Keepers
vAlve ServICe
VALVES:
STEM
FACE
45º
MARGIN
Figure 6-6. Valve
VALVE SPRING
COMPRESSOR
PIVOT
BALL
STUD
Replace valves if they are
damaged, distorted, or if the
margin is ground to less than
0.09 inch (.0mm). If the valve
is in usable condition, use a valve
grinder or Neway valve refacer
to grind the valve face to a 5º
angle. After reconditioning, the
valves should be lapped with a
suitable valve lapping tool and
valve lapping compound (see
Figure 6-6).
NOTE: Proper lapping of valves and seats will remove
grinding marks and ensure a good seal between the
valve and its seat. After lapping, be sure to remove all
lapping compound from the valve faces and seats. If
using a Neway valve and seat system it is not required
to lap the valve or seat.
VALVE SEATS:
SEAT
WIDTH
46°
Figure 6-7. Valve Seat
The recommended procedure for cutting a valve is to use
the "Neway Valve Cutting System." This type of system uses
cutters of three different degrees.
First, use the 60º cutter to clean and narrow the seat from
the bottom toward the center (see Figure 6-8).
Second, use a º cutter to clean and narrow the seat from
the top to the center.
Finally, use a 6º cutter to cut in the seat to a width of 0.09
inch (mm).
BOTTOM
NARROWING
CUTTER
TOP
NARROWING
CUTTER
NARROWING
SEAT
CUTTER
Figure 6-8. Cutting a Valve Seat. 3 Steps
6-2
Valve seats are not replace-
able. If they are burned
or pitted, they can be
reground using a grind-
ing stone or Neway Valve
Reseater. Grind seats at a
6º angle and to a width
of 0.09 inch (.0mm) (see
Figure 6-8).
15º
60º
BOTTOM
SEAT
NARROWING
46º
31º
TOP
31º
46º
TOP
NARROW
BOTTOM
NARROW