01-40B-00
CS-420ES
1
0
INTRODUCTION
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 and directions in this SERVICE
DATA are based on the latest products information available at the time of publication.
INDEX
CONTENTS
1 SERVICE INFORMATION
1-1 Specifi cation ............................................... 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
CARBURETTOR ADJUSTMENT PROCEDURE
2-1 General adjusting rules ............................... 7
2-2 Presetting idle adjust screw, L mixture needle
and H mixture needle ........................................ 7
2-3 Adjusting carburettor................................... 9
2-4 Positioning plug of air cleaner cover ......... 10
Reference No.
.............................. 2
01-40B-00
page
.. 7
ISSUED: 200801
2
1 SERVICE INFORMATION
1-1 Specifi cations
Model CS-420ES
Dimensions Length* mm(in) 393 (15.47)
Width mm(in) 245 (9.65)
Height mm(in) 277 (10.91)
Dry weight* kg(lb) 4.6 (10.1)
Engine Type KIORITZ, air-cooled, two-stroke, single cylinder
Rotation Clockwise as viewed from the output end
Displacement cm
Bore mm(in) 40.0 (1.575)
Stroke mm(in) 32.0 (1.260)
Compression ratio 6.5
Carburettor Type Diaphragm horizontal-draught with auto-return choke
Model Walbro WT-820A
Venturi size-Throttle bore mm(in) 13.50 - 15.85 (0.532 - 0.624)
Ignition Type CDI (Capacitor discharge ignition) system
Digital magneto
Spark plug BPMR8Y
Exhaust Muffl er type Spark arrestor muffl er with catalyst
Starter Type ES (effortless-start)
Rope diameter x length mm(in)
Fuel Type Premixed two-stroke fuel
Mixture ratio 50 : 1 (2 %)
Gasoline Minimum 89 octane gasoline
Two-stroke air cooled engine oil ISO-L-EGD (ISO/CD13738), JASO 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 driven type
Sprocket Type Spur
Number of teeth 7
Pitch in 0.325
Chain tensioner type Side Access
SERVICE INFORMATION
3
(in3) 40.2 (2.453)
3.0 x 950 (0.12 x 37.4)
CS-420ES
* Without guide bar and saw chain.
Cutting devices
Guide bar Type 38RD58-325 43RD58-325
Called length cm 38 45
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
CS-420ES
1-2 Technical data
Engine
Idling speed r/min 2400 - 2900
Wide open throttle speed* r/min 12300 - 13000
Clutch engagement speed r/min 3800 - 4300
Compression pressure MPa (kgf/cm
Ignition system
Spark plug gap mm(in) 0.6 - 0.7 (0.024 - 0.028)
Minimum secondary voltage at 1000 r/min kV 15
Primary coil resistance Ω 200 - 400
Secondary coil resistance kΩ 1.5 - 2.2
Pole shoe air gaps mm(in) 0.3 - 0.4 (0.012 - 0.016)
Ignition timing at 3000 r/min °BTDC 10
at 8000 r/min °BTDC 32
at 10,000 r/min °BTDC 34
at 12,000 r/min °BTDC 15
Carburettor
Idle adjust screw initial setting turns in** 1 3/8
L mixture needle initial setting turns back 1 3/8
H mixture needle initial setting turns back 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 r/min Adjustable : 1.5 - 13 (0.05 - 0.40)
mL/min(U.S.fl .oz./min) (Factory set 7 mL/min)
SERVICE INFORMATION
2
) (psi) 0.84 (8.6) (122)
3
BTDC: Before top dead centre.
* With 38/45 cm guide bar and saw chain.
**Set idle adjust screw to the point that its tip just contacts throttle plate before initial setting.
4
1-3 Torque limits
Descriptions
Starter Starter pawl M 5 40 - 60 4 - 6 35 - 50
system
Ignition Magneto rotor (Flywheel) M 8 250 - 290 25 - 29 220 - 250
system
Ignition switch M 14 15 - 30 1.5 - 3 13 - 26
Spark plug M 14 150 - 170 15 - 17 130 - 150
Fuel Carburetor M 5 30 - 45 3 - 4.5 26 - 40
system
Clutch Clutch hub LM 10 300 - 400 30 - 40 260 - 350
Engine Crankcase M 5* 70 - 110 7 - 11 60 - 95
Engine mount M 5 70 - 110 7 - 11 60 - 95
Muffl er M 5 80 - 110 8 - 11 70 - 95
Cylinder cover M 5 25 - 45 2.5 - 4.5 22 - 40
Others Auto-oiler M 4 20 - 35 2.5 - 3.5 17 - 30
Front handle M 5** 45 - 65 4.5 - 6.5 40 - 55
Rear handle assembly M 5 30 - 50 3 - 5 26 - 45
M 4 35 - 50 3.5 - 5 30 - 45
Handle lid M 4 10 - 20 1 - 2 9 - 17
Brake lever (Hand guard) M 5** 10 - 20 1 - 2 9 - 17
M 4** 45 - 65 4.5 - 6.5 40 - 55
Sprocket guard plate M 4** 10 - 20 1 - 2 9 - 17
Chain catcher M 5 45 - 60 4.5 - 6 40 - 52
Guide bar M 8 200 - 230 20 - 23 175 - 200
Regular bolt, nut and screw M 3 6 - 10 0.6 - 1 5 - 9
M 5 25 - 45 2.5 - 4.5 22 - 40
M 6 45 - 75 4.5 - 7.5 40 - 65
Starter case M 5** 25 - 35 2.5 - 3.5 22 - 30
Ignition coil M 5 40 - 60 4 - 6 35 - 50
carburetor elbow M 5** 20 - 30 2 - 3 17 - 26
Intake bellows M 5 30 - 45 3.0 - 4.5 26 - 40
M 4 15 - 25 1.5 - 2.5 13 - 22
SERVICE INFORMATION
Size
kgf•cm
N•m
CS-420ES
in•lbf
LM: Left-hand thread *Apply thread locking sealant (See below) ** Tapping screw
1-4 Special repairing materials
Material
Adhesive Ball bearing outer / crankcase
Pulse pipe joint
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)
Location
Loctite #675 or equivalent
Remarks
CS-420ES
5K173
5K280
5K174 5K190
5K016 5K042
5K277 5K278 5K279
5K275
5K276
5K191B
SERVICE INFORMATION
1-5 Service limits
ABCD
5
E
FGH
KLMP
N
Description mm (in)
A Cylinder bore When plating is worn and aluminum can be seen
B Piston outer diameter Min. 39. 89 (1.570)
C Piston pin bore Max. 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)
6
1-6 Special tools
SERVICE INFORMATION
CS-420ES
1
2
a = 3 mm
a = 4 mm
3
45
a
6
50
0.4
0.8
0
0
1.2
MPa
1.
7
8
10 11 1312
14 15
16
9
1.65
1.35
0.4
1.5
91019
#.014 = .35mm
Ignition Air Gap Gauge
P/N 91004
Key Part Number Description Reference
1 897801-33330 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 carburettor
10 897726-09130 Oil seal tool Installing oil seals
11 897800-79931 Spark tester Checking ignition system
12 897803-30133 Pressure tester Testing carburettor and crankcase leakage
13 91019 Limiter cap tool Removing and installing limiter cap
14 500-500 Welch plug tool Removing and installing welch plug tool
15 990610-00051 Loctite #515 Applying crankcase seam
16 91004 Module air gap gauge Adjusting pole shoe air gaps
CS-420ES
H
L
2 CARBURETTOR ADJUSTMENT PROCEDURE
2-1 General adjusting rules
A. Before starting the unit for adjustment, check the following items.
1. The correct spark plug must be clean and properly gapped.
2. The air fi lter element must be clean and properly installed.
3. The muffl er exhaust port must be clear of carbon.
4. The fuel lines, tank vent and fuel fi lter are in good condition and clear of debris.
5. The fuel is fresh ( > 89 octane : RON ) and properly mixed at 50 : 1 with “ISO L-EGD” or “JASO FC/
FD” 2-stroke oil.
6. The recommended bar and chain must be installed, and properly tensioned.
SERVICE INFORMATION
7
NOTE :
on the unit. Otherwise serious engine damage will occur due to overspeeding.
B. Start and run engine for two minutes alternating between WOT and idle every 5 seconds. Turn L and
H mixture needles full anticlockwise. Adjust idle speed screw to 2,650 +/- 200 r/min. If engine does not
run correctly after this adjustment, proceed to the next step 2-2.
IMPORTANT : After adjusting carburettor according to the steps 2-2 and 2-3, the limiter cap(s)
must be installed in L and H speed mixture needle(s) to comply with Emission Directive.
2-2 Presetting idle adjust screw, L mixture needle and H mixture needle
In order to achieve proper carburettor adjustment, 38 or 45 cm bar and chain should be installed
Tools Required : Small screwdriver with 2.5
mm blade, P/N 897801-33330 electronic tachometer, P/N 91019 limiter cap removal tool.
Parts Required : (2) P/N P003-000010 limiter caps.
1. Turn the L and H mixture needles anticlockwise
to rich side stop to align limiter cap tab (A) with locating slot (B), using 2.5 mm blade screwdriver.
NOTE :
(B), there is possibility of stripping the threads
made by the removal tool when removing the limiter caps.
If cap tabs (A) misalign with locating slots
B
A
A
B
(continued)
8
2-2 Presetting idle adjust screw, L mixture needle and H mixture needle (continued)
SERVICE INFORMATION
2. Screw threaded end of limiter cap removal tool
91019 with 2.5 mm left-hand thread into center
hole of limiter cap anticlockwise until tab of the limiter cap just comes out of the locating slot.
CS-420ES
NOTE :
ITER CAP FROM CARBURETTOR!
If the limiter cap is pulled out completely, there is
a chance that the other mixture needle would turn
and limiter cap tab would misalign with locating
slot when screwing the limiter cap removal tool
into center hole of the limiter cap. As a result, the
thread of the limiter cap would be stripped. Use
3 mm diameter thread wood screw to remove a
stripped limiter cap.
3. Remove the limiter cap removal tool from the
limiter cap by turning the tool clockwise, leaving
the limiter cap in place.
4. Screw threaded end of limiter cap removal tool
91019 into center hole of the other limiter cap anticlockwise until the limiter cap is removed from the
mixture needle. Remove the limiter cap from limiter
cap removal tool, and removal complete of first
limiter cap.
DO NOT COMPLETELY REMOVE LIM-
5. Turn L and H mixture needle clockwise until
lightly seated, and then turn out both mixture needles following turns.
L mixture needle : 1 3/8, H mixture needle : 2 3/4
NOTE :
damage to carburettor may occur.
6. Remove air fi lter cover and air fi lter to see that
idle speed screw contacts the throttle plate. Turn
idle adjust screw anticlockwise and set the screw
until the tip just contacts the throttle plate. Then
turn idle adjust screw 1 3/8 turns clockwise. Reinstall air fi lter, and cleaner lid.
If needles are overtighted during seating,
CS-420ES
H
L
2-3 Adjusting carburettor
SERVICE INFORMATION
9
Idle adjust screw
L mixture needle
4. Set idle engine speed to 3,800 r/min by turning idle adjust screw. Engine rpm should be stable at 3,800
+/- 50 r/min after idle adjust screw adjustment.
5. Turn L mixture needle anticlockwise reducing engine idle speed 1,200 r/min to set idle speed at 2,600
r/min. The engine idle speed ranges 2,400 - 2,800 r/min.
NOTE :
mixture needle to assure accurate tachometer readings.
6. Before adjusting H mixture needle, WOT engine speed should be less than or equal to 12,000 r/min. If
rpm is higher, turn H mixture needle anticlockwise until 12,000 r/min is achieved. To make the fi nal WOT
engine speed adjustment, turn H mixture needle clockwise in 1/8 turn increments with the engine at idle,
then squeeze throttle trigger and check WOT engine speed. The fi nal WOT engine speed should fall with-
in 12,400 - 12,800 r/min range.
Engine speed must be allowed to stabilize a minimum of 20 seconds after each adjustment of L
H mixture needle
1. Start engine and warm it up at idle for one
minute. Turn H mixture needle anticlockwise until
engine speed drops to approx. 12,000 r/min.
2. Then continue to warm up cycling engine speed
between WOT for 5 seconds, and idle for 5 seconds for another minute and a half.
NOTE :
load longer than 10 seconds, or engine damage
may occur.
3. Adjust L mixture needle to reach maximum engine rpm just before lean drop off.
Do not run engine at high speed without
7. After adjusting carburettor, screw new limiter cap on the thread of the limiter cap removal
tool 91019 (C) anticlockwise approx. 2 turns as
shown, and put the limiter caps on L and H mixture
needles respectively. And then press the caps on
L and H mixture needles with opposite side of the
limiter cap tool (C)
C
IMPORTANT : The limiter caps must be installed L and H mixture needles to comply with Emission
Directive.
8. Start engine, and verify engine idle speed ranges from 2,400 to 2,900 r/min, and WOT engine speed
ranges from 12,300 to 13,000 r/min. Make sure the chain does not rotate when engine is idling. When
fi nal adjustment is completed, the engine should idle, accelerate smoothly, and attain WOT per above
specifi cations.
NOTE :
and run the engine before fi nal carburettor adjustments are made to conform the unit to meet Emission
Directive. Actual turns required for engine operation may vary.
The initial carburettor settings for idle adjust screw, L and H mixture needles are intended to start
NOTE :
ing slots (B) in extended housing of carburettor.
Align the limiter cap’s tabs (A) with locat-
B
A
A
B
NOTE :
tions due to changing ambiant conditions, fuel, and engine loads. Safe engine rpm variances should be
within the WOT, Idle engine speed ranges listed in Section 1-1, otherwise the carburettor should be readjusted.
Engine WOT, and idle engine speed in fi eld operation may vary from fi nal adjustment specifi ca-
10
2-4 Positioning Plug of air cleaner cover
SERVICE INFORMATION
CS-420ES
When it is cold weather lower than 10
celeration is poor, change place of the plug on
air cleaner cover from closed position (normal) to
opened position.
1. Air cleaer cover on CS-420ES has plug.
2. The picture shows normal position of the plug
(A).
o
C and ac-
(A)
(B)
3. Remove the plug from air cleaner cover to open
the warm air intake and introduce warm air from
cylinder side to carburettor room. And place the
plug in holder (B) on air cleaner cover to avoid losing as shown.
NOTE :
the temperature is over 10
vapor lock.
Replace the plug to normal position when
o
C to avoid carburettor
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