Shindaiwa 300 User manual

Shindaiwa
Chain Saws
SERVICE
MANUAL
SHINDAIWA SERVICE MANUAL
$7.50

Service Manual
Shindaiwa Chain Saws
Contents Section page
1Model Designation and Identification ... 3
2Troubleshooting ...................................... 6
3Carburetors ............................................ 22
Operation ................................................. 22
Adjustment .............................................. 24
Servicing .................................................. 27
4Recoil Starters ....................................... 40
5Ignition Systems .................................... 46
Troubleshooting ....................................... 49
6Clutches ................................................. 60
7Cylinders and Pistons ........................... 70
8Engine Crankcase ................................. 80
9Mufflers ................................................... 92
10 Chain Brakes .......................................... 98
11 Oil Pumps ............................................. 108
12 Rear Handles and A/V Cushions........ 114
13 Model 357 Top Handle Saw ................ 118
14 Appendix .............................................. 128
Specifications ........................................ 128
Torque Values ........................................ 130
Metric Conversions ............................... 131
Tolerances and Wear Limits .................. 132
Fuel and Oil ........................................... 134
Special Service Tools ............................ 136
䊚Shindaiwa Inc. 1995

䊚Shindaiwa Inc. 1995
2
Attention Statements
Throughout this manual are statements
surrounded by boxes and preceded by
special symbols:
WARNING!
A statement preceded by the word
“WARNING” contains information that
should be acted upon to prevent serious
bodily injury.
ATTENTION!
A statement preceded by the word
“ATTENTION” contains information that
should be acted upon to avoid damaging
the saw.
MODEL ID
Additional statements that are not preceded
by symbols are:
IMPORTANT!
A statement preceded by “IMPORTANT” is
one that possesses special significance.

䊚Shindaiwa Inc. 1995 3
Model Designation and Identification Section 1
Chain Saws
Model 300
Model 300S
Model 360
Model 377
MODEL ID
Typical location
SHINDAIWA ENGINE
MODEL
SER.
NO.
X X X X X
X X X X X X X
ACC-20
Specifications subject to change without notice.

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Chain Saws
Section 1 Model Designation and Identification
Model 488
Model 575 (680 and 695 similar)
57701
Model 577
Model 577P
MODEL ID
Specifications subject to change without notice.

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Model Designation and Identification Section 1
Chain Saws
Model 757
Model 357
MODEL ID
Specifications subject to change without notice.
Model 757C

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6
CRK-27
Section 2 Troubleshooting The 2-Stroke Cycle Engine
Theory of
Operation
Figures 2.1 and 2.2
Spark plug
Compression/
Combustion
Exhaust and
transfer ports
closed
Intake
port
open
Crankcase
Vacuum
Figure 2.1 Crankcase vacuum is created during the
compression stroke. When the spark plug fires, the
compressed mixture above the piston ignites and
begins to expand.
Piston Ported Induction
1. Intake
As the piston moves up toward the cylinder
head, a low pressure (vacuum) is created in
the crankcase. As the moving piston uncovers
the intake port, atmospheric pressure pushes
a fresh charge of fuel-air mixture into the
crankcase.
The mixture accomplishes two functions
before it is moved to the combustion chamber:
■Oil suspended in the mixture coats all
internal engine parts including cylinder
walls, crankshaft, and bearings.
■The atomized fuel mixture absorbs heat as
it enters the crankcase, lowering the
engine’s operating temperature.
2. Compression
As the piston continues to move upward and
cover the cylinder ports, the combustion
chamber is sealed and compression begins.
The air-fuel mixture introduced during the
previous revolution’s transfer cycle is now
trapped and becomes compressed between
the piston and cylinder head.
3. Ignition
As the piston approaches the top of the
cylinder, the spark plug fires and ignites the
fuel-air mixture. To compensate for increases
in engine rpm, spark timing is advanced
electronically.
A two-stroke cycle or
“two-cycle” engine
produces one power
stroke for every
revolution of its
crankshaft. Intake
and compression
occur during the
piston’s “up” stroke;
power and exhaust
occur during the
“down” stroke.
Six distinct pro-
cesses occur during
every revolution of
the crankshaft, and a
loss or weakness of
even one of these
processes will affect
the other five.
3
2
1
TROUBLESHOOTING

䊚Shindaiwa Inc. 1995 7
Troubleshooting The 2-Stroke Cycle Engine Section 2
Figure 2.2 The burning mixture expands, forcing the
piston down and compressing the fresh mixture in the
crankcase. As the piston exposes the transfer port,
crankcase pressure forces fresh mixture into the
combustion chamber and helps push the remaining
exhaust gasses through the exhaust port.
4. Power (combustion)
The fuel-air mixture expands rapidly as it
burns, forcing the piston down the cylinder.
Piston movement is transferred to the crank-
shaft through the connecting rod, rotating the
crankshaft.
5. Exhaust
Expanding gasses continue to force the piston
downward, exposing the exhaust port. Most of
the spent combustion gasses are expelled
through the exhaust port.
6. Transfer
The piston’s downward movement covers the
intake port and uncovers the transfer port,
while simultaneously compressing the fresh
fuel-air mixture drawn into the crankcase
during Step 1. As the transfer port is uncov-
ered, the fresh mixture swirls rapidly into the
cylinder.
As the fresh fuel-air mixture enters the
cylinder, it also helps to push or
scavenge any
remaining exhaust gasses out through the
exhaust port.
CRK-26
Exhaust and
transfer ports
open
Intake port
closed
5
6
4
TROUBLESHOOTING

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Section 2 Troubleshooting The 2-Stroke Cycle Engine
Reed Valve Induction
as used on Model 357
Figures 2.3 and 2.4
1. Intake
As the piston moves up toward the cylinder
head, low pressure (vacuum) created in the
crankcase allows atmospheric pressure to
open the reed valve and push a fresh charge
of fuel-air mixture into the crankcase.
The fuel-air mixture accomplishes two
functions before it is moved to the combustion
chamber:
■Oil suspended in the mixture coats all
internal engine parts including cylinder
walls, crankshaft, and bearings.
■The atomized fuel mixture absorbs heat
from the crankcase, lowering the engine’s
operating temperature.
2. Compression
As the piston continues to move upward and
cover the cylinder ports, the combustion
chamber is sealed and compression begins.
The air-fuel mixture introduced during the
previous revolution’s transfer cycle is now
trapped and becomes compressed between
the piston and cylinder head.
3. Ignition
As the piston approaches the cylinder head,
the spark plug fires and ignites the fuel-air
mixture. To compensate for increases in
engine rpm, spark timing is advanced
electronically.
Theory of
Operation
TROUBLESHOOTING
Figure 2.3 Reed Valve Induction System (reed valve open)
CRB-75
Spark Plug
Low Pressure
1
Reed Valve Open
3
2
Combustion and
Compression Exhaust and Transfer
Ports (closed)

䊚Shindaiwa Inc. 1995 9
Troubleshooting The 2-Stroke Cycle Engine Section 2
4. Power (combustion)
The fuel-air mixture expands rapidly as it
burns, forcing the piston down the cylinder.
Piston movement is transferred to the crank-
shaft through the connecting rod, rotating the
crankshaft.
5. Exhaust
Expanding gasses continue to force the piston
downward, exposing the exhaust port. Most of
the spent combustion gasses are expelled
through the exhaust port.
6. Transfer
The piston’s downward movement com-
presses the fuel-air mixture drawn into the
crankcase during Step 1, causing the reed
valve to close. As the moving piston uncovers
the transfer port, the fresh mixture swirls
rapidly into the cylinder.
As the fresh fuel-air mixture enters the
cylinder, it also helps to push or
scavenge any
remaining exhaust gasses out through the
exhaust port.
TROUBLESHOOTING
Figure 2.4 Reed Valve Induction System (reed valve closed)
CRB-74
Spark Plug
Transfer Port
(open)
4
56
Exhaust Port
(open)
Reed Valve
Closed

Section 2 Troubleshooting
Mechanical failure of any carburetor is far less
common than problems arising from contami-
nated fuel, improper adjustment, or operator
abuse. Figure 2.5 is provided as a trouble-
shooting checklist.
IMPORTANT!
Carburetor operation is directly affected by
the quality of air and fuel entering the
carburetor! Before troubleshooting or
adjusting any carburetor, inspect fuel and
air filters for cleanliness, operation, and
proper installation!
General
Troubleshooting
Procedures
Figure 2.5 Troubleshooting Guide
䊚Shindaiwa Inc. 1995
10
CRB-89
4
910
6
7
18
5
32
TROUBLESHOOTING
1. Is the fuel tank filled with clean,
fresh fuel of the proper grade and
mixture?
2. Check for spark!
3. Compression at least 100 psi or
above?
4. Is the air filter clean and properly
installed?
5. Are the spark arrestor and muffler
clean and properly installed?
6. Inspect fuel filter, and check fuel
lines for leaks/deterioration.
Pressure-test fuel system for leaks.
7. Inspect the impulse tube or
passage for condition and
operation. Pressure-test crankcase
as required.
8. Inspect the tank vent. Clean or
replace as required
9. Reset carburetor mixture
adjustments (Section 3).
10. Pressure test the carburetor for
pop-off and reseat values.

Troubleshooting Section 2
1. Fuel
Drain all fuel into a clean container, and
discard any fuel showing visible contamination
such as dirt or water. Be especially suspicious
of fuel with an unusual odor, cloudiness, or
thickening. If the fuel is severly contaminated
or “varnished,” the carburetor and fuel system
must be completely disassembled for a
thorough inspection and cleaning. For specific
fuel recommendations and testing procedures,
see “Fuel and Oil” in the Appendix.
2. Spark (Figure 2.7)
Connect the spark plug lead to an adjustable-
gap spark tester, turn the ignition switch to the
“I” (on) position, and crank the engine vigor-
ously to test for spark. A healthy ignition
should produce a strong blue spark of nearly
1/4” length at the tester. If no spark is visible
or if the spark is weak or yellow in color, refer
to “Ignition Troubleshooting,” (Section 5).
3. Compression (Figure 2.8)
Install a reliable compression gauge, and then
crank the engine vigorously through 2-3 pulls
of the recoil starter. Compression at cranking
speeds should be at least 100 psi or above.
Compresion readings consistently below 100
psi can indicate internal engine wear or
damage (Sections 7 and 8).
4. Air Filter
Inspect the air filter, and clean or replace filter
elements as required (Figure 2.9).
■Paper-type elements should be cleaned
with compressed air only.
■All other Shindaiwa filter elements can be
washed in clean fuel mixture and then
blown dry before reinstallation.
ATTENTION!
Careless use of compressed air can
damage air filter elements. Always direct
the airstream from the inside (carburetor
side) toward the outside face of the
element. Any engine that has been run
with a damaged or incorrectly installed air
filter assembly should be carefully
inspected for internal damage from
ingested debris.
IGN-54
Figure 2.7 Checking Spark
CRB-68
Figure 2.8 Checking Compression
57721
Figure 2.9 577 Air Filter Installation
䊚Shindaiwa Inc. 1995 11
Adjustable-gap
Tester
Minimum
100 psi
Filter Element; Clean
with fuel mixture
Cover
TROUBLESHOOTING

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12
CRB-103
Section 2 Troubleshooting
General
Troubleshooting
Procedures
(continued)
5. Spark Arrestor Screen and Exhaust Port
(Figures 2.10 and 2.11)
Remove and inspect the spark arrestor
screen, and clean as required. If further
decarbonizing if necessary, refer to Section 9
(Mufflers) and Section 7 (Pistons).
IMPORTANT!
A clogged arrestor screen or muffler can
cause an engine to lose power, and may
prevent the engine from starting altogether!
6. Fuel Filter and Lines
Remove and inspect the fuel filter elements
and screens. Be especially alert for any signs
of dirt, water, or other contamination
(Figure 2.12).
IMPORTANT!
Dirt or other debris on the inner filter screen
may indicate additional debris is trapped
within the carburetor body! Trapped debris
can restrict fuel flow, possibly leading to
engine seizure!
Tug gently on the fuel line, and replace any
line showing unusual stretch or loss of elastic-
ity. Be especially alert for softened sections of
line that might collapse under suction and
“starve” the saw.
Disconnect the fuel line from the carburetor.
Plug or clamp the filter end of the line and use
Shindaiwa p/n 99909-93 to pressure test the
line for leaks (Figure 2.13).
IMPORTANT!
When servicing fuel filters, always use the
factory-recommended filter or components
for the specific model carburetor and
application! Modification, substitution, or
use of aftermarket fuel filters or components
can unbalance fuel flow within the entire
system, causing engine performance
problems!
Figure 2.13 Leak-testing the Fuel Line
10
20
30
40
50
60
0
.5
1.0
1.5 2.0 2.5
3.0
3.5
4.0
0
CRB-63
Figure 2.10 Inspect Arrestor Screen (357 shown)
Fuel Line
Fuel Filter
Clamp
35722
Muffler Screen
Cover
Figure 2.12 Fuel Filter Elements
Some early-model Walbro filters
used an inner element that re-
sembled grey wool or felt. Replace
these elements with a pair of
metal screens, p/n 22118-85460
Figure 2.11 Inspect Exhaust Port for Carbon Buildup
Carbon Buildup
on Exhaust Port
TROUBLESHOOTING
Spark Plug
Hole
Body
Retainer
Inner
Elements Element
Pressure
Gauge
p/n 99909-93
Look through
the spark
plug hole.

䊚Shindaiwa Inc. 1995 13
Troubleshooting Section 2
7. Impulse Passage/Crankcase Pressure
Test The Impulse Passage,
Models 488 and larger (Figure 2.14)
Disconnect the impulse tube from the fuel
pump, and carefully inspect the tube for
damage or deterioration.
Connect pressure guage (Shindaiwa
p/n 99909-93 or equivalent) to the impulse
tube and then crank the engine.
■A fluctuating gauge reading during crank-
ing indicates the impulse tube is clear and
is functioning properly.
■No needle movement indicates a plugged
impulse tube or possibly a crankcase leak.
or
The passage can be tested by placing a
small droplet of oil over the open end of the
impulse tube and then cranking the engine. If
the impulse passage is clear, the oil droplet
will move rapidly in and out as the engine is
cranked.
Test The Impulse Passage, Models 300
through 377 (includes 357) (Figure 2.15)
Remove the carburetor and place a small
droplet of oil over the impulse passage hole
and test as above.
IMPORTANT!
Never use gasket sealant on any gasket
installed over an impulse passage! Gasket
sealant can plug the impulse passage,
causing the engine to run lean.
Test For Crankcase Leaks
An engine with a rough or erratic idle, or one
that is unstable or “runs away” under load
may be drawing extra air through leaking
crankcase seals or gaskets.
■After blocking the intake and exhaust ports,
a gauge such as Shindaiwa p/n 72174-
99200 can be used to pressurize the
crankcase through the impulse tube or
through an adapter as shown (Figure 2.16).
■If the correct block-off plates are not
available, the ports can usually be blocked
by clamping small sections of heavy rubber
or gasket material beneath the muffler and
carburetor bases.
General
Troubleshooting
Procedures
(continued)
CRB-62
10
20
30
40
50
60
0
.5
1.0
1.5 2.0 2.5
3.0
3.5
4.0
0
Figure 2.14 Testing Impulse Passage (488 and larger)
Figure 2.16 Leak-testing with Gauge p/n 72174-99200
10
0
20
30
40
50
60
0
.5
1.0
1.5 2.0 2.5
3.0
3.5
4.0
CRK-64
Figure 2.15 Testing the Impulse
Passage (300 through 377)
CRB-64
Impulse
Tube
Needle
Fluctuates
Rapidly
Exhaust sealed
with block-off plate
Place oil
droplet here.
Pressure
Gauge
Clamp the
impulse
tube
Shindaiwa p/n
72174-99200
TROUBLESHOOTING
Steady at 4–6 psi (about .4 kg)

䊚Shindaiwa Inc. 1995
14
8. Tank Vent
Inspect the fuel tank vent for damage or
clogging, and clean or replace as required.
9. Carburetor Adjustments
Figure 2.17
Using the settings and adjustment procedures
outlined in Section 3, reset all carburetor
adjustments to factory-recommended settings.
10. Pop-off and Reseat Pressures
(metering valve)
(Figure 2.18)
Connect Shindaiwa pressure tester 99909-93
or equivalent to the carburetor fuel inlet, and
test the inlet needle assembly for proper pop-
off and reseat values.
■Reseat pressure demonstrates the
carburetor’s ability to block and regulate
typical fuel pump pressures of 5-7psi.
■Pop-off pressures can vary
considerably ,
but the inlet needle
must reseat and hold
pressure of at least 10psi.
IMPORTANT!
For accurate pressure testing, the inlet
needle must be slightly wet with fuel or
solvent.
Section 2 Troubleshooting
General
Troubleshooting
Procedures
(continued)
35715
Figure 2.17 Carburetor Adjustments (357 shown)
CRB-65
10
20
30
40
50
60
0
.5
1.0
1.5 2.0 2.5
3.0
3.5
4.0
0
Figure 2.18 Testing Pop-off and Reseat Pressure
(HDA shown)
TROUBLESHOOTING
Connect to
fuel inlet
Steady at 10 psi
or above

䊚Shindaiwa Inc. 1995 15
Troubleshooting Section 2
Troubleshooting
Guide
Does the engine
crank?
Faulty recoil starter.
Fluid in the crankcase.
Internal damage.
NO
Check
compression.
Loose spark plug.
Excess wear on
cylinder, piston, rings.
Tighten and re-test.
Refer to the Cylinders and Pistons Section.
NO
YES
Is the fuel fresh
and of the
proper grade
and mixture?
Fuel is out-dated:
may also be stale,
varnished, or
contaminated
NO
YES
Is fuel reaching
the carburetor?
(spray fuel
directly into the
carburetor
venturi to test)
Clogged fuel filter,
damaged fuel line
or impulse passage.
Clean or replace fuel system
components as required.
NO
Is there spark at
the spark plug
wire terminal?
The ignition
switch is “OFF”.
Faulty ignition ground.
Faulty spark plug lead.
Faulty ignition system.
Move switch to “ON” and re-start.
NO
YES
YES
Is the spark
plug firing
properly?
Plug is soaked with fuel.
The plug is fouled or is
improperly gapped.
Plug is internally faulty
or of the incorrect type.
Crank the engine with the plug removed;
replace the plug, and re-start.
Clean and regap the plug to 0.024"
Replace with the correct plug
(see Specifications in the Appendix)
YES
What To Check Possible Cause Remedy
THE ENGINE DOES NOT START
Refer to the Recoil Section.
Refer to the Carburetor Section.
Refer to the Engine Crankcase/
Cylinder and Pistons Sections.
Re-fill with fresh fuel of
the correct mixture
Refer to Fuels in the Appendix
NO
Flywheel key is
sheared.
NO
YES
Loose flywheel or
“thrown” chain
Replace the key and retorque
the flywheel (see Torque Values in
the Appendix)
Is the exhaust
system clean
and functioning
properly? (can
prevent the
engine from
firing)
NO
YES
Arrestor screen/cylinder
exhaust port is clogged
with carbon.
Clean or replace arrestor screen
(refer to the Muffler section).
Inspect and decarbonize exhaust
port (Cylinder and Piston section)
Refer to the Ignition Section.
TROUBLESHOOTING

䊚Shindaiwa Inc. 1995
16
Section 2 Troubleshooting
Troubleshooting
Guide
(continued)
Is the engine
overheating?
Operator is overworking
the machine.
Carburetor mixture is
too lean.
Fuel contains excessive
oxygenates.
Incorrect fuel/oil ratio.
Flywheel/cylinder fins
missing or clogged.
Air deflector or cylinder
cover missing or
damaged.
Carbon deposits in
cylinder head or
on piston.
Sharpen the saw chain.
Cut at a slower rate.
Adjust the carburetor (Carburetor section).
See also “Fuels” in the Appendix.
Inspect the boot for leakage.
Drain the fuel system and refill with the
correct fuel mixture (see the Appendix).
Clean, repair or replace components
as necessary.
Decarbonize. Refer to the Piston and
Cylinder Section.
What to Check Possible Cause Remedy
The engine
runs rough at
all speeds.
Clogged air cleaner.
Water in the fuel system.
Loose or damaged
spark plug.
Service the air cleaner.
Inspect fuel strainer and screens.
Tighten or replace spark plug as required.
The engine
knocks under
load.
Engine is overheated.
Improper fuel or fuel
mixture.
Carbon deposits in the
combustion chamber.
Refer to Overheating causes/remedies
(above).
Check fuel octane rating. Test for the
presence of alcohol or other oxygenates
in the fuel (see Fuels in the Appendix).
Decarbonize (see the Cylinder and Piston
section
)
.
LOW POWER OUTPUT
Choke is closed.
Metering needle sticking.
Faulty carburetor
diaphragm.
Black, sooty
smoke at
exhaust; may
also be
unburned fuel
at the exhaust.
Open the choke.
Disassemble and thoroughly clean the
carburetor (see Carburetor section)
TROUBLESHOOTING

䊚Shindaiwa Inc. 1995 17
Troubleshooting Section 2
Poor
acceleration.
Clogged air filter.
Spark arrestor
(carbon deposits).
Clogged fuel filter.
Carburetor mixture
incorrectly adjusted.
Idle speed
too low.
Dirt, gum, or varnish
clogging carburetor.
Clogged tank vent.
Blocked impulse passage.
Fuel line is collapsing.
Metering diaphragm is
leaking.
Spark arrestor is clogged.
Clean the element.
Decarbonize. Refer to the Muffler section.
Clean/replace fuel filter (Carburetor section).
Adjust carburetor (Carburetor section).
Adjust. Refer to the Specifications section
in the Appendix.
Overhaul the carburetor (Carburetor section).
Clean or replace vent as required.
Inspect and pressure-test lines;
replace as required (Carburetor section).
Pressure-test the carburetor; overhaul as
required (Carburetor section).
Clean/replace as required (Muffler section).
Symptom Possible Cause Remedy
Uneven idle;
engine may “run
away” at higher
throttle settings
Air leak at boot, seal, or
crankcase.
Remove and inspect boot or insulator block;
Pressure test crankcase
(Crankcase section).
Saw chain
moves at idle
speed
Idle speed too high.
Broken clutch spring.
Reset idle speed to specification (Appendix)
Replace spring, shoes as required
(Clutch section).
Excessive
vibration.
Damaged A/V cushion.
Bent crankshaft.
Damaged flywheel fins.
Fault
y
i
g
nition.
See Rear Handles and Mounts section.
See Crankcase section.
See the Recoil Starters section.
See the I
g
nition section.
ADDITIONAL PROBLEMS
TROUBLESHOOTING

䊚Shindaiwa Inc. 1995
18
Section 2 Troubleshooting
Diagnosing
Engine Seizure
Severe metal galling/
transfer all around the
piston; even scoring
Figure 2.19
Piston damaged from
lack of lubrication.
Carbon scoring
produces soft-
edged grooves
on the exhaust
side of the
piston. Piston
rings are still
free in the
grooves.
Ingested water
or snow leaves
a shiny,
polished area
on the intake
side (away
from the arrow)
Ingested debris
produces a
sandblasted
appearance or a
dull grey surface
on the intake
side of the piston
(away from the
arrow). The
piston skirt is
worn thin at the
base. Ring lands
are worn.
Figure 2.20 Operating with debris in the cylinder.
An engine can seize whenever there is metal-
to-metal contact between internal moving
parts. Most engine seizures can be traced to
at least one of the following:
Lubrication (Figure 2.19)
■Lack of oil. Insufficient or poorly mixed oil
ratio. Shindaiwa machines are designed to
use Shindaiwa Premium 2-cycle Engine Oil
at a ratio of 40:1 (3.2 ozs./U.S. gallon).
■Incorrect oil type. Generic-brands and
some outboard motor mixing oils may not
provide sufficient lubrication throughout the
broad temperature range associated with
high performance air-cooled engine
operation.
IMPORTANT!
When Shindaiwa Premium 2-cycle Engine
Oil is not available, fuel should be mixed
with a premium-grade 2-cycle mixing oil
specifically designed for use in high-
performance air cooled 2-cycle engines!
Debris (Figure 2.20)
■Excessive carbon buildup. Carbon
accumulations may be dislodged from the
exhaust port, jamming between piston and
cylinder.
■Faulty or missing air filter. Dirt, water, or
other debris enters the crankcase and
cylinder, scoring the piston and cylinder
and causing rapid component wear.
TROUBLESHOOTING
All Shindaiwa products are powered by high
performance engines that produce the most
horsepower from the lightest possible
design.
Two factors are critical to the service life
and durability of any high performance
engine:
1. Lubrication
Proper lubrication is essential for reducing
friction between an engine’s moving parts.
By reducing friction, lubrication also
helps reduce the heat developed during
normal engine operation.
Since a 2-cycle engine doesn’t have a
reservoir of oil in its crankcase, a steady
supply of high-quality lubricant must enter
the engine as part of the fuel mixture.
Refer to the Fuel and Oil Section in the
Appendix for specific fuel/oil mixture
information.
2. Cooling
Cooling any high performance engine is a
complex task. To remove the heat generated
from both friction and the combustion
process, Shindaiwa engines rely on:
■Lubricating Oil
■Air-Fuel Mixture
■Cylinder Design
■Flywheel Design
ATTENTION!
Proper lubrication and cooling are
essential to both the performance and
service life of any two-cycle engine! A
partial failure in either of these areas can
lead to engine seizure!
Factors Affecting Engine Durability

䊚Shindaiwa Inc. 1995 19
Troubleshooting Section 2
Figure 2.21 Damage caused by overheating.
Overheating causes a
piston skirt to expand
and score heavily on the
exhaust side of the
cylinder, and may
produce similar (but
reduced) scoring on the
cooler intake side as
well.
Figure 2.22 Damage caused by preignition.
Preignition typically
melts the piston crown
at the exhaust side
(toward the arrow) of the
piston, or may burn a
hole completely through
the crown. Heat causes
the piston to expand and
score at the exhaust
side, sticking rings in
their grooves.
Figure 2.23 Exhaust Gas Temperature vs
Carburetor Adjustment
1-1/4 1
Carburetor Ad
j
ustment
500°
550°
600°
650°
700°
1-1/8
Exhaust Gas Temperature
(degrees Fahrenheit)
CRB-94
Detonation results
when fuel explodes
instead of burning,
and has a hammering
effect that can crack or
pound a hole through
a piston top.
Figure 2.24 Damage caused by detonation.
Overheating (Figure 2.21)
■Operating an engine with clogged or
damaged cooling fins, or with missing
cooling system components. Overheated
internal moving parts may expand beyond
normal rates and dimensions, allowing
metal-to-metal contact.
IMPORTANT!
Overheat damage is often caused by
forcing a saw engine to cut with a dull or
improperly sharpened chain, or by failing to
select the proper size and capacity saw for
the job at hand.
■Preignition (Figure 2.22) from incorrect
spark plug/carbon buildup (may also result
from lean carburetor setting).
■Incorrect or “lean” fuel-air ratio
(Figure 2.23).
Operating an engine at an oxygen-rich
carburetor setting raises combustion
temperatures (same effect as pressing the
lever on an acetylene cutting torch).
■Air Leaks
Air leaking past crankcase seals, cylinder
gaskets, or impulse passages can dilute or
“lean out” an engine’s fuel-air ratio, and can
produce the same effect as an improperly
adjusted carburetor.
■Oxygenated fuels, any fuel containing
alcohol or ether-based oxygenating
compounds. So-called “clean air” fuels are
blended to provide additional oxygen
during the combustion process, producing
higher combustion temperatures similar to
a “lean” carburetor adjustment. For addi-
tional information on oxygenated fuels, refer
to
Fuel and Oil in the Appendix.
■Outdated or low-octane fuel can burn
unevenly, producing excessive combustion
pressures that tend to have a hammering
effect on pistons and related components
(Figure 2.24). Shindaiwa engines require a
fuel with an octane rating of at least 87 or
above. Unless fuel has been pretreated
with an approved fuel stabilizer such as
Sta-Bil™, Shindaiwa advises against using
any motor fuel stored over 30-days.
TROUBLESHOOTING