Generac Power Systems 940-2, 941-2 Valve Service, Cylinder Head Removal, Removal of Valve Spring

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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