Echo CS-370ES User manual

Ord. No. 401-29

INTRODUCTION
This service manual contains information for
service and maintenance of ECHO CHAIN
SAW, model CS-370ES, CS-420ES.
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 Catalog together
with this manual when servicing.
We are constantly working on technical
improvement of our products. For this reason,
technical data, equipment and design are
subject to change without notice. All
specifications,illustrationsanddirectionsinthis
manual are based on the latest products
information available at the time of publication.

CS-370ES
CS-420ES 1
TABLE OF CONTENTS
Page Page
1 SERVICE INFORMATION................................... 2
1-1 Specifications.................................................. 2
1-2 Technical data................................................. 3
1-3 Torque limits.................................................... 4
1-4 Special repairing materials ............................. 4
1-5 Service Limits ................................................. 5
1-6 Special tools ................................................... 6
2 STARTER SYSTEM ............................................ 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 ........................................... 14
3-1 Troubleshooting guide .................................. 15
3-2 Testing spark................................................. 16
3-3 Inspecting spark plug.................................... 16
3-4 Inspecting ignition switch.............................. 17
3-5 Replacing ignition switch .............................. 17
3-6 Inspecting ignition coil resistance................. 18
3-7 Replacing spark plug cap and coil................ 18
3-8 Replacing ignition coil................................... 19
3-9 Setting pole shoe air gaps............................ 19
3-10 Inspecting flywheel and key ......................... 20
4 FUEL SYSTEM .................................................. 21
4-1 Inspecting air filter ........................................ 22
4-2 Inspecting fuel cap and strainer ................... 22
4-3 Replacing purge bulb.................................... 23
4-4 Inspecting fuel tank and line......................... 24
4-5 Inspecting and replacing tank vent............... 25
4-6 Replacing fuel line, fuel tank vent assembly
and grommet................................................. 26
4-7 Adjusting carburetor ..................................... 27
4-7-1General adjusting rules................................. 27
4-7-2Presetting idle adjust screw, L mixture
needle and H mixture needle ....................... 27
4-7-3Adjusting carburetor ..................................... 29
4-8 Positioning plug of air cleaner cover ............ 30
4-9 Testing carburetor......................................... 31
4-10 Inspecting crankcase pulse passage ........... 31
4-11 Inspecting metering lever height .................. 32
4-12 Inspecting inlet needle valve ........................ 32
4-13 Replacing Welch plug................................... 33
4-14 Installing diaphragm ..................................... 33
4-15 Installing carburetor ...................................... 34
5 CLUTCH SYSTEM ............................................ 35
5-1 Inspecting clutch parts.................................. 35
5-2 Replacing clutch parts .................................. 36
5-3 Installing clutch assembly............................. 36
6 SAW CHAIN LUBRICATION SYSTEM............. 37
6-1 Inspecting oil cap and strainer...................... 37
6-2 Inspecting oil line .......................................... 38
6-3 Inspecting oil tank vent ................................. 38
6-4 Replacing oil line and grommet .................... 39
6-5 Disassembling auto-oiler assembly.............. 40
6-6 Replacing V-ring ........................................... 41
6-7 Assembling auto-oiler parts.......................... 42
7 ENGINE ............................................................. 43
7-1 Testing cylinder compression ....................... 44
7-2 Cleaning cooling air passage ....................... 44
7-3 Inspecting muffler and exhaust port ............. 45
7-4 Testing crankcase and cylinder sealing........ 45
7-5 Removing engine block ................................ 46
7-6 Inspecting cylinder........................................ 47
7-7 Inspecting piston and piston ring.................. 47
7-8 Inspecting crankcase and crankshaft........... 48
7-9 Replacing oil seal and ball bearing............... 48
7-10 Installing piston and piston ring .................... 49
7-11 Installing piston into cylinder ........................ 50
7-12 Installing engine block .................................. 51
8 CHAIN BRAKE SYSTEM.................................. 52
8-1 Disassembling chain brake........................... 52
8-2 Assembling brake parts ................................ 53
9 REAR HANDLE AND CONTROL SYSTEM ..... 54
9-1 Replacing throttle latch ................................. 55
9-2 Replacing cushions ...................................... 55
9-3 Replacing throttle trigger .............................. 57
10 GUIDE BAR MOUNTING SYSTEM ................ 59
10-1 Replacing chain tensioner ............................ 60
10-2 Replacing guide bar stud.............................. 60
10-3 Installing guide bar stud................................ 61
11 MAINTENANCE GUIDE .................................. 62
11-1 Service Intervals ........................................... 62
11-2 Troubleshooting guide .................................. 63
11-3 Disassembly Chart ....................................... 65
INDEX .................................................................... 66

SERVICE INFORMATION CS-370ES
CS-420ES
2
1 SERVICE INFORMATION
1-1 Specifications
Model CS-370ES CS-420ES
Dimensions Length* mm(in) 393 (15.5)
Width mm(in) 245 (9.6)
Height mm(in) 277 (10.9)
Dry weight* kg(lb) 4.6 (10.1) 4.6 (10.1)
Engine Type KIORITZ, air-cooled, two-stroke, single cylinder
Rotation Clockwise as viewed from the output end
Displacement cm3(in3) 36.3 (2.22) 40.2 (2.45)
Bore mm(in) 38.0 (1.50) 40.0 (1.58)
Stroke mm(in) 32.0 (1.26) 32.0 (1.26)
Compression ratio 7.6 6.5
Carburetor Type Diaphragm horizontal-draft, with auto-return choke**
Model Walbro WT-820A
Venturi size-Throttle bore mm(in) 13.5 - 15.85 (0.532 - 0.624)
Ignition Type Digital magneto : CDI system
Spark plug BPMR8Y
Starter Type ES (effortless)-start
Rope diameter x length mm(in) 3.0 x 950 (0.12 x 37.4)
Fuel Type Premixed two-stroke fuel
Mixture ratio 50 : 1 (2 %)
Gasoline Minimum 89 octane gasoline
Two-stroke air cooled engine oilISO-L-EGD (ISO/CD13738), JASO M345-FC/FD
Tank capacity L (U.S.fl.oz.) 0.41 (13.9)
Clutch Type Centrifugal, 3-shoe slide with 3-tension spring
Guide bar / Saw chain lubrication type Automatic with volume adjuster
Oil Tank capacity L (U.S.fl.oz.) 0.28 (9.5)
Auto oiler type Clutch related type
Sprocket Type Spur
Number of teeth 6 7
Pitch in 3/8 0.325
* Without guide bar and saw chain.
** Auto-return choke is on switch bracket.
Cutting devices CS-370ES
Guide bar Part No. 30RC50M-3/8 35RC50M-3/8
Called length cm 30 35
Gauge in 0.050
Saw chain Type OREGON 91VG
Number of drive links 47 53
Pitch in Low profile 3/8
Gauge in 0.050

SERVICE INFORMATION
CS-370ES
CS-420ES 3
1-1 Specifications (continued)
Cutting devices CS-420ES
Guide bar Part No. 38RD58-325 43RD58-325
Called length cm 38 43
Gauge in 0.058
Saw chain Type CARLTON K2L OREGON 21BP
Number of drive links 64 72
Pitch in 0.325
Gauge in 0.058
1-2 Technical data
Model CS-370ES CS-420ES
Engine
Idling speed rpm 2400 - 2900 2400 - 2900
Wide open throttle speed* rpm 11500 - 12500 12300 - 13000
Clutch engagement speed rpm 3800 - 4300 3800 - 4300
Compression pressure MPa (kgf/cm2) (psi) 1.02 (10.4) (148) 0.84 (8.6) (122)
Ignition system
Spark plug gap mm(in) 0.6 - 0.7 (0.024 - 0.028)
Minimum secondary voltage at 1000 rpm kV 15
Secondary coil resistance kΩ1.5 - 2.2
Pole shoe air gaps mm(in) 0.3 - 0.4 (0.012 - 0.016)
Ignition timing at 3,000 rpm °BTDC 10 10
at 8,000 rpm °BTDC 32 32
at 10,000 rpm °BTDC 34 34
at 12,000 rpm °BTDC 15 15
Carburetor
Idle adjust screw initial setting turns in** 1 5/8 1 3/8
L mixture needle initial setting turns back 1 1/4 1 3/8
H mixture needle initial setting turns back 2 3/8 2 3/4
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
Chain oil discharge volume at 7000 rpm Adjustable : 1.5 - 13 (0.05 - 0.40)
mL/min(U.S.fl.oz./min) (Factory set 7 mL/min)
BTDC: Before top dead center.
* With 35/38 cm guide bar and saw chain.
** Set idle adjust screw to contact throttle plate before initial setting.

SERVICE INFORMATION CS-370ES
CS-420ES
4
1-3 Torque limits
Descriptions Size kgf•cm N•m in•lbf
Starter Starter pawl M5 40 - 60 4 - 6 35 - 50
system Starter case M5** 25 - 35 2.5 - 3.5 22 - 30
Ignition Magneto rotor (Flywheel) M8 250 - 290 25 - 29 220 - 250
system Ignition coil M5 40 - 60 4 - 6 35 - 50
Ignition switch M14 15 - 30 1.5 - 3 13 - 26
Spark plug M14 150 - 170 15 - 17 130 - 150
Fuel Carburetor M5 30 - 45 3 - 4.5 26 - 40
system carburetor elbow M5** 20 - 30 2 - 3 17 - 26
Intake bellows M5 30 - 45 3.0 - 4.5 26 - 40
Clutch Clutch hub LM10 300 - 400 30 - 40 260 - 350
Engine Crankcase*** M5* 70 - 110 7 - 11 60 - 95
Engine mount M5 70 - 110 7 - 11 60 - 95
Muffler M5 80 - 110 8 - 11 70 - 95
Cylinder cover M5 25 - 45 2.5 - 4.5 22 - 40
Others Auto-oiler M4 20 - 35 2.5 - 3.5 17 - 30
Front handle M5** 45 - 65 4.5 - 6.5 40 - 55
Rear handle assembly M5 30 - 50 3 - 5 26 - 45
M4 35 - 50 3.5 - 5 30 - 45
Handle lid M4 10 - 20 1 - 2 9 - 17
Brake lever (Hand guard) M5** 10 - 20 1 - 2 9 - 17
M4** 45 - 65 4.5 - 6.5 40 - 55
Sprocket guard plate M4** 10 - 20 1 - 2 9 - 17
Chain catcher M5 45 - 60 4.5 - 6 40 - 52
Guide bar M8 200 - 230 20 - 23 175 - 200
Regular bolt, nut, M3 6 - 10 0.6 - 1 5 - 9
and screw M4 15 - 25 1.5 - 2.5 13 - 22
M5 25 - 45 2.5 - 4.5 22 - 40
M6 45 - 75 4.5 - 7.5 40 - 65
1-4 Special repairing materials
Material Location Remarks
Adhesive Ball bearing outer / crankcase
Pulse pipe joint Loctite #675 or equivalent
Cushions Loctite #424, ThreeBond #1741 or equivalent
Liquid gasket Crankcase seams Loctite #515 or equivalent
Grease Auto-oiler worm
Clutch needle bearing
Handle cushions Lithium based grease
Rewind spring
Starter center shaft
Chain brake (metal contact part) Molybdenum grease (approx. 1 gram)
LM: Left-hand thread *Apply thread locking sealant (See below) ** Tapping screw
*** The torque differences among four bolts should not exceed 20 kgf•cm (2N•m, 17in•lbf) on crankcase

SERVICE INFORMATION
CS-370ES
CS-420ES 5
Description mm (in)
CS-370ES CS-420ES
A Cylinder bore When plating is worn and aluminum can be seen
B Piston outer diameter Min. 37.91 (1.493) 39.89 (1.570)
C Piston pin bore Max. 9.075 (0.3573) 9.030 (0.3555)
D Piston ring groove Max. 1.6 (0.063)
E Piston ring side clearance Max. 0.1 (0.004)
F Piston pin outer diameter Min. 8.98 (0.3535)
G Piston ring width Min. 1.45 (0.057)
H Piston ring end gap Max. 0.5 (0.02)
K Con-rod small end bore Max. 12.025 (0.4734)
L Crankshaft runout Max. 0.05 (0.002)
M Sprocket bore Max. 13.07 (0.5146)
N Clutch drum bore Max. 71.5 (2.81)
P Sprocket wear limit Max. 0.5 (0.02)
1-5 Service Limits
5K173
5K280
5K174 5K190
5K016 5K042
5K277 5K278
5K191
5K279
1234
5K275
5K276
ABCD
FGH
KLMP
N
E

SERVICE INFORMATION CS-370ES
CS-420ES
6
Key Part Number Description Reference
1 990511-30017 Tachometer PET-1000 Measuring engine speed
2 895612-79920 L-hex wrench (3 mm) Removing and installing hex. socket bolts (M4)
3 895610-79920 L-hex wrench (4 mm) Removing and installing hex. socket bolts (M5)
4 897501-03938 Puller Removing magneto rotor
5 897505-16133 Clutch tool Removing and assembling clutch assembly
6 91037 Compression gauge Measuring cylinder compression
7 897702-30131 Piston pin tool Removing and installing piston pin
8 897701-06030 Bearing wedge Removing and crankshaft ball bearings
9 897563-19830 Metering lever gauge Measuring metering lever height on carburetor
10 897826-16131 Pressure rubber plug Testing crankcase and cylinder sealings
11 897831-16131 Pressure rubber plug Testing crankcase and cylinder sealings
12 897726-09130 Oil seal tool Installing oil seals
13 897603-23030 PTO shaft puller Removing auto-oiler cap
14 897800-79931 Spark tester Checking ignition system
15 897803-30133 Pressure tester Testing carburettor and crankcase leakage
16 91019 Limiter cap tool Removing and installing limiter cap
17 500-500 Welch plug tool Removing and installing welch plug tool
18 990610-00051 Loctite #515 Applying crankcase seam
19 91004 Module air gap gauge Adjusting pole shoe air gaps
1.35
0.4
1.65
1.5
a
20
40
60
80 120140
160
180
20
100
Ignition Air Gap Gauge
#.014 = .35mm
P/N 91004
91019
1-6 Special tools
145 2
69
10 11 1312
15 17
3
8
a = 3 mm
a = 4 mm
7
19
16 18
14

7
STARTER SYSTEM
CS-370ES
CS-420ES
Working principle
1. When starter grip is pulled, rope reel (D) rotates.
2. The rotation force of rope reel (D) is transmitted
to pawl catcher (F) by power spring (E) that is
connected with rope reel (D) and pawl catcher (F).
3. Pawl catcher (F) engages with starter pawls on
flywheel to turn crankshaft.
4. The load from compression pressure in cylinder
will keep crankshaft from rotating as power spring
(E) is twisted and accumulates energy.
5. Starter grip is pulled further; more energy is
stored in power spring (E) until the accumulated
energy is enough to overcome the compression
pressure in cylinder.
6. When accumulated energy in power spring (E)
overcomes the load from compression pressure in
cylinder, crankshaft will be rotated.
7. Power spring absorbs compression resistance of
cylinder and snatch back of engine during starting
action.
8. When starter rope is released, rope reel (D) is
returned together with power spring (E) and pawl
catcher (F) by rewind spring tension.
9. After engine starts, starter pawls pivot outward by
centrifugal force and disengage from pawl catcher
(F).
2 STARTER SYSTEM (ES starter)
(A) Starter case
(B) Rewind spring
(C) Rewind spring case assembly
(D) Rope reel
(E) Power Spring
(e) Hook end of power spring
(F) Pawl catcher
F
E
A
DC
B
e
Construction
1. Rewind spring case assembly (C) is installed
inside starter case (A).
2. Rope reel (D) with starter rope is installed on
rewind spring case assembly.
3. Hook located on the backside of rope reel
engages with end of rewind spring (B).
4. Power spring (E) is installed on rope reel.
5. Hook of power spring engages with rope reel and
top end hook (e) of power spring engages with pawl
catcher (F).

STARTER SYSTEM CS-370ES CS-420ES
8
4. Remove screw (C).
5. Remove pawl catcher (D) and power spring (E).
6. Remove rope reel (A) from starter case slowly to
prevent rewind spring (F) from unwinding.
7. Remove rewind spring case (G) from starter case.
WARNING DANGER
Wear eye protection and take care when re-
moving starter drum, because rewind spring
may unwind suddenly and cause injury to
eyes and body.
C
D
EG
A
2-1 Disassembling starter assembly
1. Remove four bolts securing recoil starter
assembly. Remove recoil starter assembly from unit.
2. Pull out starter rope about 30 centimeters (12 in)
and hold rope reel (A). Loop excess rope in rope
reel notch (B) as shown.
3. Rotate rope reel (A) counterclockwise to release
tension of rewind spring.
A
B
F

9
STARTER SYSTEM
CS-370ES
CS-420ES
4K287
C
C
C
2-2 Replacing starter rope
1. Pull out and untie knot (A).
2. Pull out knot (C) from rope reel (B).
3. When installing a new starter rope, singe both
ends of the rope to prevent fraying.
4. Make a knot (C) at end of starter rope and pass
the rope through hole of rope reel, then press the
knot (C) into reel well as shown.
5. Pass the other end of starter rope through rope
guide on starter case, then pass starter rope through
starter grip and make a knot as shown.
BA

STARTER SYSTEM CS-370ES CS-420ES
10
2. Install rewind spring case assembly on starter
case matching hole (C) with post (D). Hook (E) of
rewind spring should contact with post of starter
case.
3.Assemble rope reel (F) engaging hook (f) of rope
reel with hook (E) of rewind spring.
2-3 Assembling starter
1. If rewind spring (B) is unwound from rewind spring
case (A), wind the spring inside case as shown.
A
B
E
D
C
f
FE

11
STARTER SYSTEM
CS-370ES
CS-420ES
6. Install pawl catcher, assembling power spring
hook (J) into pawl catcher hole (I).
F
2-3 Assembling starter (continued)
4. Check for proper engagement of rewind spring
and rope reel by turning rope reel (F) clockwise and
counterclockwise.
5. Install power spring assembling hook (G) of power
spring into rope reel cutout (H).
G
H
J
I

STARTER SYSTEM CS-370ES CS-420ES
12
2-4 Replacing starter pawl
1. Remove starter assembly from unit.
2. Loosen bolt (A) and remove washer, pawl (B),
spacer (C) and torsion spring (D). Replace damaged
or worn parts.
NOTE: When it is hard to loosen bolt, use flexible
wrench 897709-79920 (E) to hold flywheel to remove
the bolt easily.
7. Fasten screw (P) on starter post.
8. Pull out starter rope inside starter case. Rotate
rope reel clockwise several turns with starter rope
hooked at notch (Q) as shown. Hold rope reel to
prevent it from rewinding and pull out starter grip to
take the rope slack.
P
Q
2-3 Assembling starter (continued)
9. Pull starter several times to check rewind spring
tension. If starter is not rewinding fully, rotate rope
reel one more turn clockwise following above step
(8).
10. Pull out starter rope all the way, and check that
rope reel can be rotated an additional half or more
turn clockwise as shown.
11. If it is less than half turn, there is a chance to
break rewind spring. In that case, reduce tension
by rotating rope reel counterclockwise one turn with
starter rope hooked at notch (Q).
A
C
B
D
E

13
STARTER SYSTEM
CS-370ES
CS-420ES
3. Install torsion spring, spacer, pawl, washer and
bolt. To avoid pinching of torsion spring, install these
parts without setting the hook (E) of torsion spring
on starter pawl. The bolt is pre-coated with sealant
on the thread. If the coat is peeled off, apply thread
locating sealant (Loctite #242, ThreeBond #1324 or
equivalent).
4. Using fine wire or hook tool (F), place hook of
torsion spring on pawl (G) as shown.
5. Make sure pawl can move smoothly. If it does not
move smoothly, check parts for correct installation.
E
G
F
2-4 Replacing starter pawl (continued)

14 IGNITION SYSTEM CS-370ES
CS-420ES
3 IGNITION SYSTEM
(A) Flywheel
(B) Ignition coil
(C) Spark plug
(D) Spark plug cap coil
(E) Spark plug cap
(F) High tension lead
(G) Primary lead
(H) Ground lead
(I) Spacer
(J) Switch bracket
(K) Throttle rod
(L) Lead terminal
(M) Ignition switch
(N) Choke knob
(O) Choke grommet
(P) Purge bulb
(A)
(B)
(C) (D)
(F)
(E)
(G)
(H)
(K)
(I)
(L) (M) (N)
(O)
(J)
(P)

15
IGNITION SYSTEM
CS-370ES
CS-420ES
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.
Not
OK OK
Not
OK
S.T.
OK
OK
Replace
ignition
coil.
Leads
connections
Not
OK
OK
OK
Not
OK
S.T.
Repair /
Replace.
Not
OK
Remedy
Inspect
Not
OK
Flywheel
key OK
R.T.*
End
Not
OK
Flywheel
magnet
Replace.
Not
OK
R.T.Not
OK
OK
OK
Replace ignition coil and / or inspect other
systems.
Replace flywheel.
OK
OK
Adjust pole shoe air gaps.
(Inspect flywheel magnet
at the same time. Go to
Aif OK.)
S.T.
Not
OK
A
S.T.: Spark test.
R.T.: Running test including actual cutting.
OK
OK
Secondary
coil
resist-
ances

16 IGNITION SYSTEM CS-370ES
CS-420ES
3-2 Testing spark
1. Remove air cleaner cover and remove spark plug
cap from spark plug.
2. Connect spark tester 990511-30023 (A) to high
tension lead and connect tester lead (B) on spark
plug.
3. Screw in adjuster (C) until the needle tips contact.
Turn out adjuster (C) 4 turns to set spark tester gap
(D) to 4 mm (0.16 in).
4. Turn ignition switch to “RUN” position. Pull starter
grip several times.
5. If spark is steady in blue or white at the tester
gap, ignition system is considered good. Go to
inspecting spark plug.
6. If no spark exists or spark is intermittent in yellow,
orange, or red, continue with further inspection.
DANGER
*Do not test near spark plug hole without
spark plug installed, otherwise there is a
chance to ignite fuel mixture inside cylinder
and cause serious personal injury.
*Do not touch metal parts of spark tester
while performing the test to avoid receiving
electrical shock.
DANGER
Do not check spark in area where gasoline is
spilled or flammable gases may exist.
3-3 Inspecting spark plug
1. Remove spark plug to inspect for fouling, cracked
or broken insulator, or rounded center electrode.
Clean or replace spark plug as required.
2. Set spark plug gap (A) by bending outer electrode
(B).
Standard : 0.6 to 0.7 mm (0.024 to 0.028 in)
3. If engine does not start after cranking several
times, inspect if spark plug is wet or dry. If it is
excessively wet or dry, inspect fuel system.
A
B
GASO
LINE
A
B
C
D

17
IGNITION SYSTEM
CS-370ES
CS-420ES
3-4 Inspecting ignition switch
1. Remove cylinder cover.
2. Connect one probe of Ohm-meter or multi-meter
to primary lead (A) and the other probe to cylinder
fin.
3. When ignition switch is in “RUN” position, tester
should indicate infinite resistance.
4. When ignition switch is in “STOP” position, tester
should show that the circuit is in conducting state
(closed circuit).
5. If ignition switch is defective, replace with a new
one.
3-5 Replacing ignition switch
1. Remove air cleaner bracket (G) and air filter.
Disconnect primary lead and ground lead from
ignition switch.
2. Disconnect throttle rod (B) from carburetor (Refer
to “9-4 Replacing throttle trigger”) and remove switch
bracket (A) from engine cover.
3. Loosen nut (C), and remove ignition switch (D)
and switch plate (E) from switch bracket (A).
4. Inspect switch plate (E) and switch bracket (A).
If damaged, replace with new parts.
5.Align notch (F) of new ignition switch with tabs of
switch plate (E) and switch bracket (A). Fasten nut
(C) on ignition switch.
6. Connect throttle rod to carburetor.
7. Put switch bracket (A) into engine cover correctly.
Connect primary lead and ground lead to ignition
switch.
A
B
BA
C
D
C
A
E
F
A
G
D

18 IGNITION SYSTEM CS-370ES
CS-420ES
3-6 Inspecting ignition coil resistance
1.Remove cylinder cover.
2. Connect one probe of Ohm-meter or multimeter
(Power source DC 1.5V) to spark plug cap coil (A).
3. Connect the other probe to cylinder (B) to
measure secondary coil resistance. Secondary
coil resistance should be in the range of 1.5 to 2.2
kΩ.
4. If the meter reading indicates infinite
resistance,remove spark plug cap and spark
plug cap coil, and measure resistance between the
conduction wire of high tension lead and ignition coil
core.
5. If the reading at step 3 or 4 is not in the range of
1.5 to 2.2 kΩ, replace with a new ignition coil (Go to
“3-7 Replacing spark plug cap and coil”).
3-7 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
removal from high tension lead (B).
3. Pull spark plug cap away from high tension lead.
4. Inspect spark plug cap coil (C) for correct
connection and corrosion. Inspect spark plug cap
for cracks. Replace as required.
NOTE: Make sure spark plug cap coil (C) contacts
conductor core of high tension lead when reinstalling
it.
5. Apply oil to spark plug cap (A) and insert high
tension lead (B) as shown until the spark plug cap
coil is properly seated in the cap.
A
A
B
C
B
A
B