Echo CS-2511TES User manual

Ref. No. 401-40
CS-2511TES
ECHO:
shindaiwa:
251Ts 251TCs
(Serial number: 37000001 and after)

INTRODUCTION
This service manual contains information for ser-
vice and maintenance of ECHO CHAIN SAW,
model CS-2511TES, shindaiwa CHAIN SAW,
model 251Ts and 251TCs
For systematic diagnosis, to avoid extra work,
time loss and to meet Emission regulation,
please refer to “Troubleshooting guide” that
describes problems, testing, remedies and
references. We recommend you make use of
Operator’s Manual and Parts Catalogue together
with this manual when servicing.
We are constantly working on technical improve-
ment of our products. For this reason, technical
data, equipment and design are subject to
change without notice. All specications, illustra-
tions and directions in this manual are based on
the latest product information available at the
time of publication.

TABLE OF CONTENTS
CS-2511TES
251Ts, 251TCs 1
CONTENTS
1 SERVICE INFORMATION ������������������������������������2
1-1 Specications......................................................2
1-2 Technical data.....................................................3
1-3 Torque limits........................................................4
1-4 Special maintenance materials...........................4
1-5 Service limits.......................................................5
1-6 Special tools .......................................................6
2 STARTER SYSTEM (ES-start / S-start) ��������������7
2-1 Disassembling starter assembly .........................8
2-2 Replacing starter rope ........................................9
2-3 Assembling starter ............................................10
2-4 Replacing starter pawl ......................................12
3 IGNITION SYSTEM ��������������������������������������������13
3-1 Troubleshooting guide .......................................14
3-2 Testing spark.....................................................15
3-3 Inspecting spark plug........................................16
3-4 Replacing spark plug cap and coil.....................16
3-5 Inspecting ignition switch ..................................17
3-6 Replacing ignition switch ..................................17
3-7 Replacing ignition coil .......................................22
3-8 Setting pole shoe air gaps ................................23
3-9 Inspecting yweel and key................................23
4 FUEL SYSTEM ��������������������������������������������������25
4-1 Inspecting air lter.............................................26
4-2 Replacing air cleaner cover latch......................28
4-3 Inspecting fuel cap and fuel strainer .................28
4-4 Inspecting fuel tank and line .............................29
4-5 Inspecting and replacing tank vent ...................30
4-6 Replacing purge bulb........................................32
4-7 Replacing fuel line and fuel return line..............33
4-8 Adjusting carburetor ..........................................35
4-8-1 General adjusting rules ..................................35
4-8-2 Initial setting Throttle adjust screw, L mixture
needle and H mixture needle...................................35
4-8-3 Adjusting carburetor .......................................36
4-9 Testing carburetor .............................................37
4-10 Inspecting crankcase pulse passage ..............38
4-11 Inspecting metering lever height......................38
4-12 Inspecting inlet needle valve ...........................39
4-13 Inspecting diaphragm and others....................40
4-14 Replacing welch plug ......................................40
4-15 Installing carburetor.........................................41
5 CLUTCH SYSTEM ���������������������������������������������42
5-1 Inspecting clutch parts ......................................42
5-2 Replacing clutch parts ......................................44
5-3 Installing clutch assembly .................................44
6 CHAIN BRAKE SYSTEM �����������������������������������45
6-1 Replacing brake lever and torsion spring .........45
6-2 Inspecting chain brake parts.............................47
7 SAW CHAIN LUBRICATION SYSTEM �������������� 49
7-1 Inspecting oil cap and strainer .......................... 49
7-2 Inspecting oil tank vent...................................... 50
7-3 Inspecting and replacing oil line........................ 51
7-4 Inspecting worm gear ....................................... 52
7-5 Cleaning and replacing auto-oiler assembly..... 53
8 ENGINE �������������������������������������������������������������� 56
8-1 Testing cylinder compression............................ 57
8-2 Cleaning cooling air passages.......................... 58
8-3 Inspecting mufer and exhaust port.................. 59
8-4 Testing crankcase and cylinder sealings ........... 60
8-5 Removing engine block .................................... 61
8-6 Inspecting cylinder ............................................ 62
8-7 Inspecting piston and piston ring ...................... 63
8-8 Replacing oil seal.............................................. 64
8-9 Inspecting crankcase and crankshaft ............... 65
8-10 Replacing oil seal and ball bearing.................. 66
8-11 Assembling crankshaft and crankcase ............ 67
8-12 Installing piston ring and cylinder .................... 68
9 HANDLE AND CONTROL SYSTEM ����������������� 69
9-1 Replacing lifting hook ........................................ 70
9-2 Replacing throttle control parts.......................... 72
9-3 Replacing front handle and spring..................... 73
9-4 Replacing rear handle and springs.................... 74
10 GUIDE BAR MOUNTING SYSTEM ����������������� 77
10-1 Replacing nut for xing guide bar................... 77
10-2 Replacing chain tensioner.............................. 78
10-3 Replacing guide bar stud................................ 79
11 MAINTENANCE GUIDE������������������������������������ 80
11-1 Troubleshooting guide ..................................... 80
11-2 Disassembly chart ........................................... 82
11-3 Service intervals .............................................. 83

SERVICE INFORMATION
CS-2511TES
251Ts, 251TCs
2
1 SERVICE INFORMATION
1-1 Specications
Dimensions Length* mm(in) 243 (9.57)
Width mm(in) 205 (8.07)
Height mm(in) 196 (7.72)
Dry weight* kg(lb) 2.3 (5.1)
Engine Type YAMABIKO, air-cooled, two-stroke, single cylinder
Rotation Clockwise as viewed from the output end
Displacement cm3(in3) 25.0 (1.525)
Bore mm(in) 35.0 (1.378)
Stroke mm(in) 26.0 (1.024)
Compression ratio 7.9
Carburetor Type Diaphragm horizontal-draught with separated primer
Model
Walbro WT-1153 (CS-2511TES)
WT-1155 (251Ts, 251TCs)
with Large D-shaped mixture needles
Venturi size-Throttle bore mm(in) 11.11-14.3 (0.437-0.563)
Ignition Type CDI (Capacitor discharge ignition) system
Digital magneto
Spark plug CMR7H
Starter Type ES (effortless)-start / S(Soft)-start
Rope diameter x length mm(in) 3.0 x 720 (0.12 x 28.3)
Fuel Type Premixed two-stroke fuel
Mixture ratio 50 : 1 (2 %)
Petrol Minimum 89 octane petrol
Two-stroke air cooled engine oilISO-L-EGD (ISO/CD13738), JASO FC/FD
Tank capacity L (UK..oz.) 0.19 (6.7)
Exhaust Mufer type Spark arrester mufer with catalyst
Clutch Type Centrifugal type, 3-shoe slide with 3-tension spring
Guide bar / Saw chain lubrication type Adjustable automatic oil pump
Oil Tank capacity L (UK..oz.) 0.14 (4.9)
Auto oiler Type Clutch related type
Sprocket Type Spur
Number of teeth 6 (Sprocket nose bar), 8 (Carving bar)
Pitch in 3/8 (Sprocket nose bar), 1/4 (Carving bar)
Spike Option (Parts number: P200-000150)
* Without guide bar and saw chain.
Cutting devices Sprocketnosebar Carvingbar
Guide bar
Type
C20S91-35SA C25S91-40SL C30S91-47ML C20H25-52CL
C25H25-60CL
:CS-2511TES only
C25H25-60CLD
Called length cm 20 25 30 20 25
Gauge in 0.050
Saw chain Type Carlton N1C-BL
OREGON 91PX OREGON 25AP
Number of drive links 35 40 47 52 60
Pitch in 3/8 1/4
Gauge in 0.050

SERVICE INFORMATION
CS-2511TES
251Ts, 251TCs 3
1-2 Technical data
Engine
Compression pressure MPa (kgf/cm2) (psi) 1.03 (10.5) (150)
Clutch engagement speed r/min 4,400
Engagement Minimum†r/min 3,900
Ignition system
Spark plug gap mm(in) 0.6 - 0.7 (0.024 - 0.028)
Spark test
Tester gap w/ spark plug mm(in) 4.0 (0.16)
Tester gap w/o spark plug mm(in) 6.0 (0.24)
Pole shoe air gaps mm(in) 0.3 - 0.4 (0.012 - 0.016)
Ignition timing at 1,000 r/min °BTDC 9
at 3,000 r/min °BTDC 12
at 10,000 r/min °BTDC 29
Carburettor
Test Pressure, minimum MPa (kgf/cm2) (psi) 0.05 (0.5) (7.0)
Metering lever height mm(in) 1.65 (0.06) lower than diaphragm seat
Tool to adjust mixture needles
Screwdriver 2.5 mm P/N X603-000050
D-shaped tool (L) P/N X645-000031
(Carb. adjustment tool P/N Y089-000094)
Carburettor adjustment
1) Initial setting
H mixture needle turn out 2 5/8
L mixture needle turn out 1 7/8
Throttle adjust screw turn in*11 5/8
Engine warm-up Idle - WOT : Total sec. 5 - 5 : 100
2) Find idle maximum speed Adjust L mixture needle to maximum idle speed*2
3) Set idle maximum speed w/ TAS r/min 4,000
4) Set idle speed
by turning L mixture needle ACW r/min 3,200 (2,800 - 3,600)
5) Conrm H mixture needle position
before WOT setting*3
Turn H mixture needle ACW to conrm engine
speed decreses less than 12,000 r/min
6) WOT setting Turn H mixture needle CW and set engine speed
within 12,400 - 12,600 r/min
7) Final WOT setting Turn H mixture needle CW by : 1/4
within 12,700 - 13,400 r/min
Chain oil discharge volume Adjustable: 1.5 - 13 (0.05 - 0.46)
(Factory set: 7 mL/min)
mL/min(UK..oz./min)
BTDC: Before top dead centre. WOT: Wide open throttle ACW: Anticlockwise TAS: Throttle adjust screw
†If clutch engagement speed is lower than minimum clutch engagement speed, replace clutch assembly with
new one.
*1Set Throttle adjust screw to the point that its tip just contacts throttle plate before initial setting.
*2If clutch engages during adjustment process 2), decrease engine speed by turning TAS ACW until clutch
disengages and then redo 2).
*3With 25 cm guide bar and properly tensioned saw chain.

SERVICE INFORMATION
CS-2511TES
251Ts, 251TCs
4
1-3 Torquelimits
Descriptions Size kgf•cm N•m lbf•in
Starter Starter pawl M 5 30 - 45 3 - 4.5 25 - 40
system Starter case M 4 20 - 30 2 - 3 20 - 25
Ignition Flywheel (Magneto rotor) M 8 250 - 290 25 - 29 220 - 255
system Ignition coil M 4* 30 - 45 3 - 4.5 25 - 40
Ignition switch M 3* 3 - 5 0.3 - 0.5 3 - 4
Spark plug M 10 100 - 150 10 - 15 90 - 135
Fuel Carburettor M 5 30 - 45 3 - 4.5 25 - 40
system
Intake bellows M 4 30 - 45 3 - 4.5 25 - 40
Clutch Clutch hub LM 8 250 - 290 25 - 29 220 - 255
Engine Crankcase M 4 30 - 45 3 - 4.5 25 - 40
Cylinder M 4 30 - 45 3 - 4.5 25 - 40
Engine mount M 4 30 - 45 3 - 4.5 25 - 40
Mufer M 5 60 - 90 6 - 9 55 - 80
Mufer cover M 4 20 - 30 2 - 3 20 - 25
Others Auto-oiler M 4 30 - 45 3 - 4.5 25 - 40
Rear handle lid M 4 20 - 30 2 - 3 20 - 25
Front handle (front side) M 5 30 - 40 3 - 4 25 - 35
Front handle (rear side) M 4 20 - 30 2 - 3 20 - 25
Spring M 4 20 - 35 2 - 3.5 20 - 30
Brake cover M 4 20 - 30 2 - 3 20 - 25
Sprocket guard plate
(Sprocket guard side) M 4 20 - 30 2 - 3 20 - 25
Brake lever (Hand guard) M 5 30 - 45 3 - 4.5 25 - 40
Chain catcher M 5 30 - 45 3 - 4.5 25 - 40
Stud bolt M 8* 150 - 200 15 - 20 130 - 220
Bolt (at guide bar mount) M 5 30 - 45 3 - 4.5 25 - 40
Guide bar nut M 8 120 - 150 12 - 15 105 - 135
Regular bolt, nut and screw M 3 6 - 10 0.6 - 1 5 - 9
M 4 15 - 25 1.5 - 2.5 13 - 22
M 5 25 - 45 2.5 - 4.5 22 - 40
LM: Left-hand thread *Apply thread locking sealant described in “1-4 Special repairing materials”
1-4 Specialmaintenancematerials
Material Location Remarks
Thread locking sealant Stud bolt Loctite #272 or equivalent
Ignition coil ThreeBond #1344 or equivalent
Ignition switch ThreeBond #1324 or equivalent
Grease Recoil starter
EPNOC AP2 (Lithium based grease)
P/N X695-000060
Needle bearing, clutch
Worm gear
Auto-oiler
Oil seal lip
Chain brake (metal contact part) Molybdenum grease (approx.1 gram)

SERVICE INFORMATION
CS-2511TES
251Ts, 251TCs 5
1-5 Servicelimits
ABCD
F G H
K L M P
N
E
Description mm (in)
A Cylinder bore When plating is worn and aluminium can be seen
BPiston outer diameter Min. 34. 92 (1.375)
CPiston pin bore Max. 8. 035 (0.3163)
DPiston ring groove Max. 1. 3 (0.051)
EPiston ring side clearance Max. 0. 1 (0.004)
FPiston pin outer diameter Min. 7. 98 (0.3142)
GPiston ring width Min. 1. 15 (0.045)
HPiston ring end gap Max. 0. 5 (0.02)
KCon-rod small end bore Max. 11. 03 (0.4341)
LCrankshaft runout Max. 0. 02 (0.001)
MSprocket bore Max. 13. 07 (0.5146)
NClutch drum bore Max. 53. 5 (2.11)
PSprocket wear limit Max. 0. 5 (0.02)

SERVICE INFORMATION
CS-2511TES
251Ts, 251TCs
6
Key Part Number Description Reference
1 G310-000050 Tachometer PET-304 Measuring engine speed
2 Y089-000094 Carb. tool KIT Adjusting carburetor
3X645-000031 D-shaped tool (L) Adjusting D
-shaped L / H mixture needle
4X603-000050 Screwdriver (2.5mm) Adjusting throttle adjust screw
5X602-000340 Torx wrench (T27) Removing and installing Torx bolt
6 897800-79931 Spark tester Checking ignition system
7 Y089-000111 Puller Removing magneto rotor and crankcase
8 91004 Module air gap gauge Adjusting pole shoe air gaps
9 897803-30133 Pressure tester Testing carburetor and crankcase leakage
10 897563-19830 Metering lever gauge Measuring metering lever height on Carburetor
11 500-500 Welch plug tool Removing and installing welch plug tool
12 P021-044870 PTO shaft puller Removing plug from auto-oiler assembly
13 91037 Compression gauge Measuring cylinder compression
14 X681-051690 Adapter (M10) Measuring cylinder compression(for 10mm dia. spark plug)
15 897826-16131 Pressure rubber plug Plugging intake port to test crankcase / cylinder leakages
16 897827-16131 Pressure plate Plugging intake port to test crankcase / cylinder leakages
17 91041 Pressure rubber plug Plugging intake port to test crankcase / cylinder leakages
18 A131-000160 Pressure connector(M10) Checking crankcase and cylinder leakages
19 91139 Pressure tester Testing tank vent and crankcase leakages
20 897726-09130 Oil seal tool Installing oil seals
21 897701-14732 Bearing tool Removing and installing crankcase ball bearings
22 897702-30131 Piston pin tool Removing and installing piston pin
1-6 Specialtools
Ignition Air Gap Gauge
#.014 = .35mm
P/N 91004
0
1
2
3
4
5
6
7
1.35
0.4
1.65
1.5
PET-304
Made in Germany
T27x200
4 0 1 0 5 5 7 8 6 9 7 4 5
1 2 5
4
3
6 7
8 9 11 1210
13 14 15 16
18 20 2119
17
22

STARTER SYSTEM
CS-2511TES
251Ts, 251TCs 7
2 STARTER SYSTEM (ES-start / S-start)
(A) Starter case
(B) Fan cover
(C) Rewind spring
(D) Rewind spring case
(E) Rope reel
(F) Power spring
(G) Pawl catcher
(H) Screw
(J) Starter rope
(K) Starter grip
Workingprinciple
1. When starter grip (K) is pulled, rope reel (E)
rotates.
2. The rotation force of rope reel (E) is transmitted
to pawl catcher (G) by power spring (F).
3. Pawl catcher (G) engages with starter pawls on
ywheel to turn crankshaft.
4. The load from compression pressure in cylinder
will keep crankshaft from rotating as power spring
(F) is twisted and accumulates energy.
5. As starter grip (K) is pulled further, more energy
is stored in power spring (F) until accumulated
energy is enough to overcome compression
pressure in cylinder.
6. When accumulated energy in power spring (F)
overcomes the load from compression pressure in
cylinder, crankshaft is rotated.
7. Power spring (F) absorbs compression resistance
of cylinder and snatch back of engine during starting
action.
8. When starter rope (J) is released, rope reel (E)
is returned together with power spring (F) and pawl
catcher (G) by rewind spring tension.
9. After engine starts, starter pawls pivot outward by
centrifugal force and disengage from pawl catcher
(G).
Construction
1. Rewind spring (C) and rewind spring case (D)
are installed inside starter case (A).
2. Rope reel (E) with starter rope (J) is installed
on rewind spring case assembly.
3. Hook located on the backside of rope reel
engages with end (c) of rewind spring (C).
4. Power spring (F) is installed on rope reel (E).
5. Hook(f1) of power spring (F) engages with
hook (e) of rope reel (E) and top end hook (f2) of
power spring (F) engages with pawl catcher (G).
(B)
(C)
(D)
(E)
(G)
(H)
(A)
(K)
(J)
(c)
(f2)
(F) (e)
(f1)

STARTER SYSTEM
CS-2511TES
251Ts, 251TCs
8
2-1 Disassemblingstarterassembly
1. Remove three bolts and remove starter assem-
bly (A) from unit.
2. Remove fan cover (B) from starter assembly (A).
3. Pull out starter rope about 30cm (12in) and hold
rope reel (C) by hand. Loop excess rope in rope
reel notch (c) as shown.
4. Rotate rope reel (C) counterclockwise to release
tension of rewind spring.
5. Remove screw (D).
6. Remove pawl catcher (E) and power spring (F).
7. Remove rope reel (C) from starter case (G)
slowly to prevent rewind spring (H) from unwind-
ing.
8. Remove rewind spring case assembly (J) from
starter case (G).
WARNING DANGER
Weareyeprotectionandtakecarewhen
removingropereel.Rewindspringmayun-
windsuddenlyandcausepersonalinjury.
A
C
D
E
H
J
G
c
F
C
B
A

STARTER SYSTEM
CS-2511TES
251Ts, 251TCs 9
2-2 Replacingstarterrope
1. Pull out and untie knot (A).
2. Pull knot (B) to remove rope from rope reel (C).
4. Make a knot (D) at end of starter rope and pass
the rope through hole of rope reel (C), then press
the knot (D) into recess as shown.
3. When installing a new starter rope, singe both
ends of the rope to prevent fraying.
5. Pass the other end of starter rope through start-
er case, from inside to outside.
6. Pass starter rope through starter grip (E). Make
a knot as shown.
7. Tighten knot (F). Push the knot (F) into recess of
starter grip (E).
4K287
A
B
C
DD
F
C C
E

STARTER SYSTEM
CS-2511TES
251Ts, 251TCs
10
2-3 Assemblingstarter
1. If rewind spring (A) is unwound from rewind
spring case (B), wind the spring (A) inside case (B)
as shown.
NOTE : Apply small amount of lithium based
grease to rewind spring case (B), before wind the
spring.
2. Carefully install rewind spring case assembly
(C) on starter case, matching hole (c) with post (D).
Hook (a) of rewind spring should contact with post
(E) of starter case.
3. Wind the rope (G) on rope reel (F) 2 turns as
shown.
4. Apply small amount of lithium based grease to
starter case side (f1) of the rope reel (F).
5. Assemble rope reel (F) engaging hook (f2) with
hook (a) of rewind spring.
AB
E
D
c
C
F
f2
a
a
f2
f1 F
G

STARTER SYSTEM
CS-2511TES
251Ts, 251TCs 11
F
2-3 Assembling starter (Continued)
6. Check for proper engagement of rewind spring
and rope reel (F) by turning rope reel (F) clockwise
and counterclockwise.
7. Apply small amount of lithium based grease to
power spring mounting groove (f3) of the rope reel
(F).
8. Install power spring (H), engaging hook (h1) with
rope reel groove (f4).
9. Install pawl catcher (J), engaging hole (j) with
power spring top end hook (h2).
10. Reinstall screw (K) on starter post.
11. Pull out starter rope inside starter case. Rotate
rope reel (F) clockwise 3 turns with starter rope
hooked at notch (f5) as shown. Hold rope reel (F)
to prevent it from unwinding and pull out starter
grip to take the rope slack.
12. Pull starter several times to check rewind
spring tension. If starter is not rewinding fully, in-
crease spring tension by rotating rope reel (F) one
more turn clockwise following above step 11.
f4
f3
J
j
K
F
f5
H
h1
h2

STARTER SYSTEM
CS-2511TES
251Ts, 251TCs
12
13. Pull out starter rope all the way, and check that
rope reel (F) can be rotated an additional half or
more turn clockwise as shown, to prevent rewind
spring from breaking.
14. If rope reel (F) can not be turned clockwise,
reduce tension by rotating rope reel (F) counter-
clockwise one turn with starter rope hooked at
notch (f5).
15. Reinstall fan cover to starter case.
16. Reassemble starter assembly to unit.
2-3 Assembling starter (continued)
c
1. Remove starter assembly from unit.
2. Loosen bolt (A) and remove pawl (B) and torsion
spring (C). Replace damaged or worn parts.
NOTE: When it is hard to loosen bolt, install clean
rope (D) in spark plug hole (E) to stop crankshaft
rotation and remove bolt easily.
3. Install torsion spring (C), pawl (B), and bolt (A).
To avoid pinching of torsion spring (C), install these
parts without setting the end (c) of torsion spring (C)
on starter pawl.
4. Using ne wire (F) or appropriate tool, place the
end (c) of torsion spring (C) on pawl (B), by hook-
ing and passing under pawl as shown.
5. Make sure pawl (B) can move smoothly. If it
does not move smoothly, check parts for correct
installation.
2-4 Replacing starter pawl
F
C
B
A
E
D
B
A
F
c
B

IGNITION SYSTEM
CS-2511TES
251Ts, 251TCs 13
3 IGNITION SYSTEM
(A) Ignition switch
(B) Spark plug
(C) Spark plug cap coil
(D) Spark plug cap
(E) Ignition coil
(F) Bolt (M4)
(G) Collar
(H) Flywheel
(J) Nut (M8)
(K) Woodruff key
(B)
(C)
(D)
(E)
(H)
(J)
(F)
(A)
(G)
(K)

IGNITION SYSTEM
CS-2511TES
251Ts, 251TCs
14
3-1Troubleshootingguide
Not
OK
Not
OK
Not
OK
OK
OK
OK
Spark plug
Spark
plug cap/
coil
Ignition
switch
Clean /
Regap /
Replace.
Replace.
Start
OK
OK
S.T.
Not
OK
S.T.
Not
OK
Not
OK
S.T.
OK
S.T.
Not
OK Pole
shoe air
gaps
Replace.
OK
OK
Leads
connections
Not
OK
OK
OK
Not
OK
S.T.
Repair /
Replace.
Not
OK
Remedy
Inspect
Not
OK
Woodruff
key
End
Not
OK
Flywheel
magnet
Replace. R.T. OK
OK
Replace ignition coil and / or inspect other systems.
Replace flywheel.
OK
OK
S.T.
S.T.: Spark test.
R.T.: Running test including actual cutting.
OK
Adjust pole shoe air gaps.
S.T.
OK
Not OK
Not
OK Not
OK

IGNITION SYSTEM
CS-2511TES
251Ts, 251TCs 15
3-2 Testingspark
1. Unhook ring (A) with screwdriver (B) or equiva-
lent and open cap cover (C).
2. Remove spark plug cap (D) from spark plug (E).
3. Connect spark plug cap (D) to spark tester
897800-79931 (F), and connect spark tester lead
(G) on spark plug (E) as shown.
4. Screw in adjuster (f1) until the needle tips con-
tact. Turn out adjuster (f1) 4 turns to set spark
tester gap (f2) to 4 mm (0.16 in).
5. Turn ignition switch to “RUN” position. Pull start-
er grip several times.
6. If spark is steady blue or white at the tester gap,
ignition system is considered good.
7. If no spark exists or spark is intermittent in
yellow, orange, or red, continue with further inspec-
tion.
WARNING DANGER
*Donottest nearsparkplughole without
spark pluginstalled,otherwisethere isa
chancetoignitefuelmixtureinsidecylinder.
*Donot touchmetal partsofsparktester
whileperformingthetesttoavoidreceiving
electricalshock.
*Donotchecksparkinareawheregasoline
isspilledorammablegasesmayexist.
GASO
GASO
LINE
LINE
A
B
C
DEG
f1
f2
F

IGNITION SYSTEM
CS-2511TES
251Ts, 251TCs
16
3-3 Inspectingsparkplug
1. Remove spark plug to inspect for fouling,
cracked or broken insulator, cracked outer elec-
trode, or rounded center electrode. Clean or
replace spark plug as required.
2. Set spark plug gap (A) by bending outer elec-
trode (B).
Standard : 0.6 to 0.7 mm (0.024 to 0.028 in)
NOTE: Take care not to crack outer electrode
when bending.
3. If engine does not start with correct spark plug,
inspect if spark plug is wet or dry. If it is exces-
sively wet or dry, inspect fuel system.
A
B
3-4Replacingsparkplugcapandcoil
1. Disconnect spark plug cap (A) from spark plug.
2. Apply some oil in spark plug cap (A) for easy re-
moval from high tension lead (B).
3. Pull spark plug cap away from high tension lead.
4. Inspect spark plug cap coil (C) for corrosion
and correct connection. Inspect spark plug cap for
cracks. Replace as required.
NOTE: Make sure spark plug cap coil (C) contacts
center core of high tension lead when reinstalling
it.
5. Coat end of high tension lead (B) with small
amount of oil, and insert it into spark plug cap (A)
as shown, until the spark plug cap coil is properly
seated in the cap.
A
B
C
A
B

IGNITION SYSTEM
CS-2511TES
251Ts, 251TCs 17
3-5 Inspectingignitionswitch
1. Remove starter assembly from unit.
2. Connect one probe of Ohm-meter or multi-meter
to ignition switch terminal (A). Connect the other
probe to another ignition switch terminal (B).
3. When ignition switch is “RUN” position, tester
should indicate innite resistance.
4. When ignition switch is in “STOP” position, tes-
ter should show that the circuit is in conducting
state (closed circuit).
5. If ignition switch is defective, replace with a new
one.
B
A
E
C
D
B
3-6 Replacingignitionswitch
{Removing}
1. Remove starter assembly from unit.
2. Remove bolt (A), ignition switch terminal (B) and
(C) from ignition coil (D).
3. Insert screwdriver or equivalent between dust
cover (E) and engine cover, and pry dust cover (E)
away from engine cover.
A

IGNITION SYSTEM
CS-2511TES
251Ts, 251TCs
18
3-6 Replacing ignition switch (Continued)
4. Loosen nut (F) and remove sprocket guard (G).
5. Remove bolt (H), chain catcher (J), and sprocket
guard plate (K)
6. Remove bolt (L) and brake lever (M).
7. Remove plug (N) and bolt (P).
8. Remove bolt (Q) and rear handle lid (R).
F
G
H
K
J
P
N
Q
R
M
L