Valve Service; Valve; Valve Seats - Generac Power Systems GN190H Service And Repair Manual

TO PREVENT EYE INJURY, ALWAYS WEAR EYE PRO-
TECTION WHEN REMOVING VALVE SPRINGS.
5. Support the valves with your fingers while compressing the valve
springs with your thumbs on the valve spring retainer (see Figure 9.5).
a. With the spring compressed, slide the larger hole of the valve
spring retainer toward the valve stem.
b. When the larger retainer hole is around the valve stem, release
the valve spring.
c. Remove the retainer, spring and washer.
Figure 9.5 — Compressing Valve Springs
6. Remove the intake and exhaust valves.
7. Clean all parts.
a. Remove carbon from the valve heads and stems.
b. Inspect valves and valve seats.
c. Service parts as outlined under "Valve Service."

VALVE SERVICE

VALVE:

STEM
FACE
45º
MARGIN
Figure 9.6
Replace valves if they are
damaged, distorted or if
the the margin is ground
to less than 0.039 inch
(1mm).
If valves are in usable con-
dition, grind or cut the valve
faces to a 45º angle (see
Figure 9.6).

VALVE SEATS:

SEAT
WIDTH
Figure 9.7
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 9.8).
Second, use a 31º cutter to clean and narrow the seat from
the top to the center.
Finally, use a 46º cutter to cut in the seat to a width
of 0.039 inch (1mm).
BOTTOM
NARROWING
CUTTER
BOTTOM
NARROWING
TOP
NARROWING
CUTTER
TOP
NARROWING
SEAT
CUTTER
TOP
NARROW
Figure 9.8 — Cutting a Valve Seat
33
SECTION 9: VALVE TRAIN
Valve seats are not replace-
able. If they are burned or
pitted, they
reground using a grinding
46"
stone or Neway Valve
Reseater. Grind seats at a
46º angle and to a width of
0.039 inch (1 mm) (see
Figure 9.7).
15º
60º
SEAT
46º
31º
31º
46º
BOTTOM
NARROW
can be