Club Car Carryall 300 2021, Maintenance And Service Manual

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67
Disassembly/Inspection and Service
17 690 15 Rev. -- KohlerEngines.com
Piston and Rings Inspection
Scuffi ng and scoring of piston and cylinder wall occurs
when internal engine temperatures approach welding
point of piston. Temperatures high enough to do this are
created by friction, which is usually attributed to improper
lubrication and/or overheating of engine.
Normally, very little wear takes place in piston boss-
piston pin area. If original piston and connecting rod can
be reused after new rings are installed, original pin can
also be reused but new piston pin retainers are required.
Piston pin is included as part of piston assembly – if pin
boss in piston or pin are worn or damaged, a new piston
assembly is required.
Ring failure is usually indicated by excessive oil
consumption and blue exhaust smoke. When rings fail,
oil is allowed to enter combustion chamber where it is
burned along with fuel. High oil consumption can also
occur when piston ring end gap is incorrect because
ring cannot properly conform to cylinder wall under this
condition. Oil control is also lost when ring gaps are not
staggered during installation.
When cylinder temperatures get too high, lacquer and
varnish collect on pistons causing rings to stick, which
results in rapid wear. A worn ring usually takes on a
shiny or bright appearance.
Scratches on rings and piston are caused by abrasive
material such as carbon, dirt, or pieces of hard metal.
Detonation damage occurs when a portion of fuel charge
ignites spontaneously from heat and pressure shortly
after ignition. This creates 2 fl ame fronts, which meet
and explode to create extreme hammering pressures on
a specifi c area of piston. Detonation generally occurs
from using low octane fuels.
Preignition, or ignition of fuel charge before timed spark
can cause damage similar to detonation. Preignition
damage is often more severe than detonation damage.
Preignition is caused by a hot spot in combustion
chamber such as glowing carbon deposits, blocked
cooling fi ns, an improperly seated valve, or wrong spark
plug.
Replacement pistons are available in STD bore size,
and 0.25 mm (0.010 in.) oversize. Replacement pistons
include new piston ring sets and new piston pins.
Replacement ring sets are also available separately for
STD, and 0.25 mm (0.010 in.) oversize pistons. Always
use new piston rings when installing pistons. Never use
old rings.
Some important points to remember when servicing
piston rings:
1. Cylinder bore must be deglazed before service ring
sets are used.
2. If cylinder bore does not need reboring and if old
piston is within wear limits and free of score or scuff
marks, old piston may be reused.
3. Remove old rings and clean up grooves. Never
reuse old rings.
4. Before installing new rings on piston, place top 2
rings, each in turn, in its running area in cylinder
bore and check end gap. Refer to Specifi cations.
5. After installing new compression (top and middle)
rings on piston, check piston-to-ring side clearance.
Refer to Specifi cations. If side clearance is greater
than specifi ed, a new piston must be used.
Piston and Rings
Inspection
Piston and Rings Components and Details
C
D
E
F
B
A
A
Top Compression
Ring
B
Middle Compression
Ring
C Oil Control Ring D Top Rail
E Expander Ring F Bottom Rail
Install New Piston Rings
Piston Ring Orientation
E
A
D
B
C
A Top Oil Rail Gap B Bottom Oil Rail Gap
C Middle Ring Gap D
Oil Ring Expander
Gap
E Top Ring Gap