Generac Power Systems 941-2 - Manual (Page 83)

Section 5.1
ENGINE OIL SYSTEM
INTRODUCTION TO OIL SYSTEM
The engine oil system serves to (a) reduce friction
between parts, (b) cool the engine, and (c) establish a
slightly negative pressure in the crankcase to prevent
oil leakage. Major components that will be discussed
in this section include the following:
• Oil Pickup Screen.
• Oil Pump.
• Crankshaft Oil Seals.
• Pressure Relief Valve.
• Breather Assembly.
• Oil Sump.
• Oil Filter Support Assembly.
OIL FLOW
See Figure 1. The oil pump draws oil from the oil
sump through an oil pickup screen and delivers it to
the areas requiring lubrication as follows:
1. Through a cored channel in the oil sump to the crankcase jour-
nal at one end of the crankshaft.
2. Through the hollow camshaft to the camshaft bearing.
3. Through a cored passage in the crankcase to the crankshaft
journal.
4. Through the crankshaft to the crankpin and connecting rod
bearing.
Figure 1. Oil System Diagram
OIL PICKUP SCREEN
DESCRIPTION:
The oil pickup screen consists of a cylindrical screen
which is open at one end only. The screen's open end
fits over a tubular protrusion in the oil sump, just
behind the oil filter support. Also see "Oil Filter
Support Assembly".
INSPECTION:
To gain access to the screen, remove the oil filter
support and its gasket. Pull the screen off its tubular
protrusion. Clean the screen in solvent, then inspect
for damage. Replace the screen if necessary.
OIL PUMP
DESCRIPTION:
The oil pump is of the trochoid type. Its inner rotor
rotates on a shaft provided in the camshaft bore of
the oil sump. The outer rotor is installed over two
drive pins on the end of the camshaft and is driven by
camshaft rotation.
Figure 2. Oil Pump
INSPECTION:
See Figure 3. Inspect the inner and outer rotors of the
pump for damage and wear. Use a feeler gauge to
check tip clearance of the rotor (measured on the
shaft in the oil sump). Check the bore inner diameter
and the thickness of the inner rotor. If wear limits are
exceeded, replace the appropriate part(s).
PUMP TIP CLEARANCE
(MEASURED ON SHAFT IN OIL SUMP)
DESIGN CLEARANCE: 0.0000-0.0010 inch
(0.000-0.025mm)
WEAR LIMIT: 0.004 inch (0.105mm) Maximum
INNER PUMP ROTOR BORE
DESIGN BORE: 0.354-0.355 inch (9.000-9.019mm)
WEAR LIMIT: 0.357 inch (9.034mm) Maximum
INNER ROTOR THICKNESS
DESIGN THICKNESS: 0.312-0.315 inch (7.95-8.00mm)
WEAR LIMIT: 0.311 inch (7.90mm) Minimum
Replace any part that is damaged or worn excessive-
ly. The shaft on which the inner rotor rotates is NOT
replaceable (oil sump must be replaced).
Page 5.1-1