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Table of Contents
CYLINDER BLOCK, PISTONS
Compression measurement
A compression
test is useful in determining
the
condition
of
the engine.
Low
compression
may be
due
to cylinder
wear; worn piston
ring grooves;
worn,
broken, or
sticking piston
rings;
poor valve
seating;
cylinder head leaks; or
damage to
the engine such as
piston
se.
i zu
re.
Too
high
compression may
be due
to
carbon built-up on
the piston
heads and
cylinder
head.
Difference
in
compression between
the
cylinders
may
cause
poor running.
Before measuring
compresison,
check
that the cylinder
head is tightened down with the
specifjed torque
{Pg.
46} and that
the
battery is
fully charged (Pg. 156)
and thoroughly
warm
up
the
engine so that engine oil
between the pistons and
cylinder walls
will
help seal
compression
as
it
does during normal
running.
While
the
engine is
running,
check
that there
is no gas
leakage
from
around
the
cylinder head
gasket
and
from
the
spark plugs.
Stop the engine, remove the spark
plugs,
and att,1.ch
the
compression
gauge
(special tool) firmly
into one
spark
plug
hole.
Using
the
starter motor, turn
the
engine
over with
the
throttle fully
open until the
com-
pression gauge
stops
rising; the
compression is the
highest reading obtainable.
Repeat the
measurement
for the
other
cylinder.
A. Compression Gauge (57001-221, 57001-1018)
Table H26
Cylinder Compression*
Usable Range
8.4 -
13.0 kg/cm
2
(119 -185
psi), and
less than
1 kg/cm
2
{14
psi)
difference between
the
cylinders
*Engine hot,
spark plugs removed, throttle fully
opened,
cranking
the
engine with
the
starter motor.
If cylinder compression
is
higher than
the usable
range, cl:leck
the following:
1.
Carbon
build-up
on
the
piston head and cylinder
head
-
clean
off
any
carbon on the
piston
head
and
cylinder
head.
2. Cylinder
head
gasket,
cylinder base
gasket - use
only
the
proper gasket for
the cylinder
head. The
use
of
a gasket of incorrect thickness will
change
the compression.
MAINTENANCE-ENGINE
127
3. Valve
stem
oil seals
and
piston rings
- rapid carbon
accumulation
in
the
combustion
chambers may
be
caused
by damaged valve stem oil seals and/or dam-
aged piston
oil
rings.
This may
be indicated by white
exhaust smoke.
4.
Cylinder
head volume (Pg.121).
If
cylinder compression is
lower than
the usable
range,
check
the following:
1. Gas
leakage
around the cylinder head
-
replace the
damaged gasket
and check
the cylinder head
warp
(Pg. 121
).
2. Condition of
the valve
seating
(Pg.
124}.
3.
Valve clearance (Pg. 16}.
4. Piston/cylinder clearance, piston seizure
5.
Piston ring,
piston
ring
groove
Cylinder, piston wear
Since there is a
difference in cylinder
wear in differ-
ent
directions,
take
a
side-to-side and
a
front-to-back
measurement at
each
of the
3
locations (total of 6
measurements}
shown
in Fig. H41.
If any
of
the
cylinder
inside diameter measurements
exceeds
the
usable range, the cylinder will have to be
bored to
oversize and then
honed.
However, if
the
amount
of
boring necessary would make the
inside diameter greater
than 56.000
mm, the
cylinder block
must be replaced.
Cylinder Inside Diameter Measurement
E
E
0
E
E
0
lJ"l
E
E
0
N
Table H27
Cylinder Inside Diameter
Standard
Usable Range
55.000 - 55.012
mm,
55.10
mm,
or
more
and
less than 0.01
mm
than
0.05
mm differ-
difference
between
any
ence
between
any
two
measurements
two measurements
.
Measure the outside
diameter of each piston 5 mm
up from the
bottom of the piston
at
a right
angle to
the direction
of the
piston pin.
If the
measurement
is
under
the
service limit,
replace the piston.

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   Also See for Kawasaki Z250 1981

This manual is also suitable for:

Kz350 1981

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