Buell XB9R 2003, Service Manual, Page: 267 / 566

3-76 2003 Buell XB9R: Engine
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CRANKCASE BREATHING SYSTEM 3.11
GENERAL
See Figure 3-114. Pressure created in the flywheel area on
piston downstroke is released through the reed valve into the
gearcase. From there a mixture of crankcase air and oil mist
is vented up the push rod covers to the upper rocker box.
See Figure 3-115. Air is allowed to escape the rocker boxes
by exiting the positive crankcase vent (PCV) valves (4)
located on top of the rocker boxes. From the PCV valves the
air enters the crankcase breather hoses (2 & 3). The crank-
case breather hoses route through the air cleaner base plate
(1) to the air box where it is directed inside the air filter ele-
ment and back into the engine.
The oil mist collects and eventually returns to the crankcase
through oil passageways in the cylinder head.
Figure 3-114. Reed Valve Assembly in Gearcase
8661
Figure 3-115. Crankcase Breathing System,
1. Base plate, air box
2. Breather hose, rear
3. Breather hose, front
4. PCV Valves (2)
5. Grommet
6. Rocker cover, top (2)
3
2
4
5
1
6
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