Service Manual
8-1
PISTON, PISTON RING, AND CON-ROD
Section
8
PISTON, PISTON RING, AND
CON-ROD
PISTON AND CON-ROD REMOVAL
To Analyze Piston Ring Wear:
1.
2.
3.
4.
Remove any carbon
or
ridge
at
the top of
cyl. bore; this will help prevent piston rings
from breaking.
To
remove piston and con-rod from engine,
rotate crankshaft (A) to expose con-rod bolts
(B)
as
shown.
Remove rod bolts and con-rod cap.
Push piston and con-rod out through the top
of cylinder.
To
Remove Piston From Con-Rod:
(1)
Remove piston pin snap rings with thin nose
pliers and slide out piston pin.
CAUTION:
Do
not reuse snap rings once removed.
Removal weakens and deforms the rings.
(2)
Remove piston rings one
at
a
time, by slipping
them over (A) ring lands. Use
a
ring expander
(A) to prevent damage to rings and piston.
(1)
Rings of the wrong
size
or
rings having im-
proper end gap will not conform to the shape
of cylinder. This results in high oil consump-
tion and excessive blow-by.
Ring end gaps should be staggered on piston
during installation. End gaps in alignment can
cause oil consumption and blow-by.
Light scuffing
or
scoring of both rings and
piston occurs when unusually high friction
and combustion temperatures approach the
melting point of piston material. Probable
causes of this condition one:
Lack of cylinder lubrication.
Improper combustion.
Wrong bearing
or
piston clearance.
Too much oil in crankcase causing fluid
Dirty cooling shroud and cyl. head.
friction.
(2)
An engine operating
at
abnormally high tem-
peratures may cause varnish, lacquer
or
carbon
deposits to form in the piston grooves making
the rings stick.
When this happens, excessive oil consumption
and blow-by will occur.
Engine overheating and ring sticking
is
usual-
ly
caused by one
or
more of:
Overloading.
Incorrect ignition timing.
Lean fuel mixture.
Dirty cooling fins.
Incorrect oil.
Low oil supply.
Stale
fuel.
(3)
Vertical scratches across piston rings are due
to an abrasive in engine. Abrasives may be
airborne, may have been left in engine during
overhaul
or
may be loose lead and carbon
deposits.
Damaged, collapsed
or
improperly installed
Loose connection
or
damaged gasket between
Air leak around carburetor-to-cyl. block
gas-
Air leakage around throttle shaft.
Failure to properly clean cyl. bore after
Scratches across oil side rails (A) are due to
When this exists, check for one
or
more of:
air cleaner.
air cleaner and carb.
/-
ket.
reconditioning engine.
abrasive in engine oil.