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3-16 2007 Dyna: Engine
OIL PRESSURE INDICATOR LAMP
See Figure 3-13. The red OIL PRESSURE indicator lamp illu-
minates to indicate improper circulation of the engine oil. The
lamp illuminates when the ignition is ﬁrst turned on (before
the engine is started), but should be extinguished once the
engine is running.
If the oil pressure indicator lamp remains lit, always Figure 3-13. Oil Pressure Indicator Lamp
check the oil supply ﬁrst. If the oil supply is normal and
the lamp is still lit, stop the engine at once and do not
ride further until the trouble is located and the necessary
repairs are made. Failure to do so may result in engine
If the indicator lamp is not extinguished, it may be the result of
a low oil level or diluted oil supply. In freezing weather, the oil
feed and return lines can clog with ice or sludge. A problem in
the lamp wiring, faulty oil pressure sending unit, damaged oil
pump, plugged oil ﬁlter element, incorrect oil viscosity, broken
or weak spring in the oil pressure relief valve and/or damaged
or incorrectly installed O-rings in the engine may also cause
the indicator lamp to remain on.
To troubleshoot the problem, always check the engine oil level
ﬁrst. If the oil level is OK, determine if oil returns to the pan
from the oil return hose. If oil does not return, shut off the
engine until the problem is located and corrected.
2007 Dyna: Engine 3-15
BREATHER OPERATION 3.6
The crankcase breather system relieves crankcase pressure
produced by the downstroke of the pistons and allows crank-
case vapors vacated from each cylinder to be directed into
the air ﬁlter element. Through effective recirculation of crank-
case vapors, the system serves to eliminate the pollutants
normally discharged from the crankcase.
See Figure 3-12. As each piston pushes downward on its
power and intake stroke, displaced air in the ﬂywheel com-
partment is vented through the crankshaft roller bearing into
the cam compartment and then up the push rod covers (1)
into the rocker housing.
Air rushes under the rocker arm support plate, which is ele-
vated slightly, and passes through an opening at the bottom
of the plate to enter the breather bafﬂe compartment (2).
In the bafﬂe compartment, the ﬂow of air passes upward
through the oil ﬁlter gauze, where the oil is removed from the
air. Two pin holes in the rocker arm support plate act as drain
holes to rid the bafﬂe compartment of the oil separated from
Passing through the oil ﬁlter gauze, the ﬂow of air passes
through the umbrella valve (3) into the breather compartment. 1
The ﬂaps of the umbrella valve only allow air to be vented one
way, rising to allow the passage of air, but then falling back
1. Push rod cover
into place to seal the vent holes as the ﬂow of air stops.
2. Breather bafﬂe
In the breather compartment, the ﬂow of air reverses direction 3. Umbrella valve
passing downward through holes aligned in the breather baf- 4. Air cleaner backplate bolt
ﬂe, rocker arm support plate and rocker housing. Exiting the 5. Breather tube
rocker housing, the air enters a passageway cast into the top
of the cylinder head. Proper orientation of the rocker housing Figure 3-12. Breather Air Flow
gasket is critical for effective sealing of this passageway.
Flowing through the cylinder head passageway, the air passes
through a drilling in the air cleaner backplate bolt (4) and then
through a breather tube (5) into the air ﬁlter element.
Air cleaner mounting without installation of the breather tubes
allows crankcase vapors to be vented into the atmosphere in
violation of legal emissions standards.