Generac Power Systems 941-2 - Manual (Page 42)

Section 2.2
VALVE TRAIN
Figure 4. Cylinder Head Removal
DANGER! ALWAYS WEAR SAFETY GLASSES
WHEN REMOVING THE VALVE SPRINGS.
5. See Figure 5, next page. Hold the valve with your fingers while
compressing the spring with your thumb, then proceed as fol-
lows:
a. While the spring is compressed, slide the larger
hole of the valve spring retainer toward the
valve stem.
b. With the larger spring retainer hole around the
valve stem, release the spring.
c. Remove the valve spring retainer, the spring
and the spring washer.
Figure 5. Removal of Valve Spring
6. Remove the intake and exhaust valves.
7. Clean all parts. Remove carbon from valve heads and stems.
8. Inspect the valves and valve seats. Service parts as outlined
under "Valve Service".
VALVES:
Replace valves If they are damaged, distorted or if
the margin is ground to less than 0.039 inch (1.0mm).
If the valves are in useable condition, use a valve
grinder to grind the faces to a 45' angle. Check valve
stem diameter.
After the valves have been reconditioned, they should
be lapped with a suitable lapping tool and valve lap-
ping compound.
VALVE SERVICE
NOTE: Proper lapping of valves and valve seats
will remove grinding marks and ensure a good
seal between the valve and its seat. Be sure to
clean lapping compound from the valve seats and
faces.
VALVE MARGIN (GV-220)
DESIGN MARGIN: 0.034-0.04 inch (0.87-1.13mm)
WEAR LIMIT: 0.020 inch (0.50mm) Maximum
INTAKE VALVE STEM DIAMETER (GV-220)
DESIGN DIAMETER: 0.274-0.275 inch (6.965-0.980mm)
WEAR LIMIT: 0.273 Inch (6.934mm) Minimum
EXHAUST VALVE STEM DIAMETER (GV-220)
DESIGN DIAMETER: 0.273-0.274 inch (6.945-6.960mm)
WEAR LIMIT: 0.272 inch (6.909mm) Minimum
NOTE: Design sizes and wear limits of valve train
components can also be found in Part 9 of this
Manual ("SPECIFICATIONS & CHARTS").
VALVE SEATS:
Valve seats are NOT replaceable. If burned or pitted,
seats can be reground. Grind seats at a 45' angle and
to a width of 0.039 inch (1.Mm).
Figure 7. Valve Seat
VALVE SEAT WIDTH GV-220)
DESIGN WIDTH: 0.034-0.044 inch (0.87-1.13mm)
WEAR LIMIT: 0.064 inch (1.63mm) Maximum
VALVE GUIDES:
Valve guides are permanently installed in the cylinder
head and cannot be replaced. If the guides become
worn beyond the wear limit, they can be reamed to
accommodate a 0.020 inch (0.50mm) oversize valve
stem. Use a straight shank hand reamer or a low
speed drill press to ream valve guides.
VALVE GUIDES (GV-220)
DESIGN DIAMETER: 0.237-0.2364 inch (6.02-6.005mm)
WEAR LIMIT: 0.238 inch (6.045mm) Maximum
!
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