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Ball Bearing, Needle Bearing; Muffler; Oil Breather; Oil Seal Damage - Kawasaki KZ400 Service Manual

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Oil Breather
The oil breather is located on the top o f the crank-
case. The front right side o f the breather opens to the
crankcase, while the upper part connects through the
breather hose to the dir cleaner.
Its function i s to
m i n i m i ~ e crankcase pressure variations caused by crank-
shaft dnd piston movement and t o recycle blowby gas.
Gas blowby is combustion chamber gas which have
escaped past the rings into the crankcase.
A small
amount i s unavoidable, b u t gas blowby increases as
cylinder wall and piston ring wear progresses.
I f not
efficiently removed, blowby gas will seriously contami-
nate the engine oil.
Recycling blowby gas means more efficient combus-
tion b u t the oil mist resulting from transmission gear
movement must first be removed.
The mixture o f
blowby gas and oil mist passes the breather, which
separates most o f the oil from the gas. The oil which is
separated from the gds returns t o the bottom o f the
crankcase. The gas is drawn through the breather hose
into the air cleaner housing, and from there, through the
carburetors into the engine.
I f the breather hose or the pdrts inside the breather-
become clogged, pressure mdy build up i n the crankcase
and cause oil leaks.
NOTE: I f the engine i s overfilled with engine oil, mist
f r o m the excess oil will go through the oil breather t o
clog the air cleaner and cause carburetion trouble. This
is n o t the fault o f the oil breather.
Ball bearing wear, damage
Since the ball bearings are made to extremely close
tolerances, the wear must be judged b y feel rather than
by measurement.
Clean each bearing in a high flash-point solvent, dry
it (do n o t spin it while it i s d r y ) , and oil it. Spin it by
hand t o check its condition. If i t is noisy, does n o t spin
smoothly, or has any rough spots, replace it.
Needle bearing wear, damage
The rollers in the needle bearings wear so little that
the wear i s difficult to measure.
Instead, inspect the
bearings for abrasion, color change, or other damage. I f
there is any doubt as to the condition o f either bearing,
replace it.
Oil seal damage
Inspect the oil seals, and replace any i f the lips are
misshapen, discolored (indicating the rubber has dete-
riorated), hardened, or other wise damaged. Since an oil
seal is nearly always damaged on removal, any removed
oil seals must be replaced. When pressing i n an oil seal
which i s marked, press it in with the mark facing out-
Press the seal in so that the face o f the seal is
level with the surface o f the hole.
The mufflers reduce exhaust noise and conduct the
exhaust gases back away from the rider while keeping
power loss to a minimum.
I f much carbon is built up
inside the muffler, exhaust efficienty is reduced, which
lowers the engine power output.
I f there is any exhaust leakage where the mufflers
connect to the cylinder head, or i f the gaskets appear
damaged, replace the gaskets. I f either muffler i s badly
damaged, dented, cracked or rusted, replace it with a
new one.
The crankshaft oil seal in the right engine cover
forms a seal between the crank chamber and the contact
breaker point cavity.
I f this seal i s damaged, oil will
leak into the contact breaker point cavity, and foul the
contact breaker points.
Any damaged, hardened, or
otherwise defective oil seal will allow oil t o leak.


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