Onan T260G Service Manual page 15

Circumferential grooves in the main bearings supply
oil to connecting rod bearings through drilled pas-
-.,sages from each main journal. A drilled passage
\connects the front main bearing oil supply t o the front
'camshaft bearing; rear cam bearing is splash lubrica-
ted. Oil overflow from the bypass valve provides
lubrication to the camshaft drive gears.
Normal oil pressure should be 30 psi (207 kPa) or
higherwhen the engine is at normal operating temper-
ature. If pressure drops below this value at governed
speed, inspect oil system for faulty components.
Check oil pump thoroughly for worn parts. Oil pump
to prime it before reinstalling. Except for gaskets and
pick-up cup, component parts of the pump are not
available individually. Install a new pump assembly if
any parts are worn.
Oil By-Pass Valve
The by-pass valve (located to the right and. behind gear
cover, Figure 5) controls oil pressure by allowing
excess oil to flow directly back to the crankcase.
Normally the valve begins to open about 20 psi
(138 kPa).
The valve is non-adjustable and normally does not
need maintenance. Determine if valve is operating
normally by inspecting plunger action as follows:
1 . Remove the 3/8 x 24 x 7/8 cap screw located
behind gear cover and under governor arm.
2. Remove spring and plunger with a magnet tool.
3. Determine proper valve operation by checking
the spring and plunger according to the following
measurements.
Plunger Diameter.. 0.3105 to 0.3125 in.
(7.89 to 7.94 mm)
Spring
Free Length.. 1.00 inch (25.4 mm)
Load 2.6Ifr0.2 Ibs. (11.6+0.9N)
when compressed to 0.5 inch (12.7 mm)
4. Check the valve seat and clean away any accumu-
lation of metal particles which could cause erratic
valve action. Verify that the valve seat is not damaged.
5. Clean plungerand spring in parts cleaning solvent
and install.
FIGURE 5. BY-PASS VALVE
6-3