Onan MJA Series Service Manual page 65

63 OIL SYSTEM
3.5.6 OIL FILTER
The full-flow filter is mounted on the filter plate at the left front corner
of the crankcase.
It
requires periodic replacement normally every 200
hours of operation. Remove the filter by turning counterclockwise with
both hands or a filter wrench. Oil the new gasket and then install a new
filter; turn it hand tight plus 1/4 to 1/2 turn.
3.5.7 CRANKCASE BREATHER
The crankcase breather, located in the rear left corner of the crank ­
case maintains a partial vacuum in the crankcase during operation to
control oil loss and ventilate the crankcase.
It
includes a metal filter
packed into the tube on the crankcase, a rubber cap with flapper valve,
and hose connecting
it
to the engine air horn.
NOTE: The MJC does not
have a flapper
valve.
To disassemble, remove
the rubber cap from the
crankcase tube and pry
the valve out of the cap.
Wash the valve in fuel at
regular intervals and
if
defective, replace it.
At the same time pull
the baffle out of the
breather tube and cle.an
it. Install the valve with
the perforated disc
toward the engine.
FIG 3.5.D - CRANKCASE BREATHER