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BBC Under Deck Components Operation
(cont'd)
The upper pulley sheave is secured to the rotating
shaft. It will always turn with the crankshaft.
The lower pulley sheave
is mounted on a bearing
which spins freely on the crankshaft, thus the two
sheaves are both mounted on the crankshaft, yet can
spin freely with respect to one another. However, once
a belt is properly tensioned in the groove created, the
two sheaves spin
as
one.
Getting more specific, the upper sheave
of the pulley
is the BBC flywheel, and the lower sheave and bearing
block are the bearing block and brake drum. The
BBC
belt fits in between these two components. The belt
is
tensioned by the brake plate assembly. Some things
to note regarding the VP BBC system is that the BBC
flywheel uses a taper
fit
to secure
it
to the crankshaft.
It
is that taper fit which keeps
it
from rotating on the
crankshaft once the crankshaft nut is tight. The small
tabs on the self-propel pulley do not assist
in this
function. (They are provided only to allow tightening
and loosening of the crankshaft nut with hand tools.)
The brake drum bearing block, screen, blade spacer,
blade and anti-scalp cup all rotate as an assembly.
Their orientation can be clearly seen in the Figure
95.
Note the vibration dampeners, two of which are used
on the BBC brake drum. These dampeners help
reduce the screeching sound when the brake is
applied, due to the bell shaped brake drum.
BBC
Cover and Screen:
The BBC cover and screen are
two important components that keep dirt and debris
out of the BBC mechanism. The screen (see Figure
92)
is installed, sharp edge down, to allow air to be drawn
in through the screen panel on top of the deck and
down underneath the deck. This venting improves the
airflow underneath the deck thereby improving quality
of cut and bagging performance. Be sure to clean the
screen on occasion, especially if quality of cut
or
bagging performance has degraded.
Before troubleshooting the BBC deck mechanism, be
sure that
it
is adjusted properly. See BBC -Adjustment,
page
X X .
BBC Under Deck Components Disassembly
1.
Stop the engine and disconnect the spark plug
lead to prevent accidental starting.
2.
Remove the 2 flanged nylon locknuts securing
the blade to the bearing block and remove the
anti-scalp cup, the blade, the blade spacer, and
the lower BBC screen. See Figure
93.
3 .
4.
5.
6.
7.
8.
9.
Figure
93
Remove the
4
flanged head self-tapping screws
securing the lower BBC cover to the housing,
and remove the lower BBC cover.
Before disassembling further, check
to make
sure that the BBC components are functioning
normally. Make sure that the brake and brake
drum fully disengage when the control bar is
cocked, then raised. Make sure that the BBC
flywheel and the brake drum rotate together
when the control bar is raised. Make sure that the
belt loosens properly when the control bar
is
lowered. Repair or replace parts as required.
If further disassembly is required, begin by
removing the crankshaft nut.
NOTE: Be careful not to damage the bearing seal
when removing this nut, or premature bearing
failure could result.
Pivot the brake plate counterclockwise slightly
and remove the bearing block and brake drum
from the crankshaft.
Again, pivot the brake plate counterclockwise
and remove the BBC flywheel.
BBC Belt
or
Idler Pulley Replacement: If the BBC
belt or idler pulley requires replacement,
it
can
be done without removal
of the brake plate.
Remove the idler pulley capscrew and nylon
locknut then pull the belt and pulley from the
brake plate as an assembly.
NOTE: The powdered metal hubs of the pulley
are replaceable, however, the bearing inside the
idler pulley is not replaceable separately.
If the brake pad has reached its service life
or
if
the brake plate has been damaged, remove the
other capscrew securing the brake plate to the
Vacu-Power Mower
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