Buell P3, Service Manual

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2007 Buell P3: Engine 3-55
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CRANKCASE BREATHING SYSTEM 3.10
GENERAL
See Figure 3-94. On piston downstroke, a mixture of crank-
case air and oil mist is vented up the push rod covers to the
upper rocker box. Air is allowed to escape the rocker box by
exiting the positive crankcase vent valve located on top of the
rocker box.
The oil mist collects and eventually returns to the crankcase
through oil passageways in the cylinder head.
The crankcase air passes through the breather assembly to
the positive crankcase vent valve (PCV) located on top of the
rocker box cover. From the PCV the air enters the crankcase
breather hose. The crankcase breather hose splits with one
hose (crankcase breather hose) going to the air cleaner and
the other hose (crankcase breather drain hose) going to the
footrest support bracket. Crankcase air is routed to the air
cleaner box where it is directed into the carburetor’s venturi.
Any residual oil drains to the crankcase breather drain hose
located behind the right footrest support (located by the oil
tank drain hose). The crankcase breather drain hose should
be drained at each oil change.
Figure 3-94. Crankcase Breathing System
1. Positive crankcase vent valve (PCV)
2. Crankcase breather hose
3. Carburetor venturi
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