Page 1
10-42A-00
SRM-420ES
SERVICE DATA
TRIMMER/BRUSHCUTTER
1
1
ECHO:
SRM-420ES
STAGE MODEL
(Serial number : 37000001 and after)
INTRODUCTION
We are constantly working on technical im-
provement 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 product information available at the time of publication.
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
and H mixture needle
2-3 Adjusting carburettor................................... 8
.......................................... 7
.............................. 2
page
.. 7
needle
Reference No.
ISSUED: 201204
10-42A-00
Page 2
2
1 SERVICE INFORMATION
1-1 Specifi cations
Model
Dimentions*
Dry weight* kg (lb)
Engine Type YAMABIKO, air-cooled, two-stroke, single cylinder
Carburettor Type Rotary type : Diaphragm, horizontal-draught, with primer
Ignition Type
Exhaust Muffl er type Spark arrester muffl er with catalyst
Starter Type ES (effortless-start)
Fuel** Type Premixed two-stroke fuel
Clutch Type Centrifugal, 2-shoe pivot
Handle Type
Drive shaft Type Solid type with serration (10-tooth)
Gear case Reduction ratio 1.33
Cutter Type Nylon line cutter 3-tooth blade (255 mm)
Length mm (in)
Width mm (in)
Heigh mm (in)
Rotation Anticlockwise as viewed from the output end
Displacement cm
Bore mm (in) 40.0 (1.58)
Stroke mm (in) 33.0 (1.30)
Compression ratio 6.7
Model WALBRO WT-1046
Spark plug BPMR8Y
Rope diameter x length mm (in) 3.8 x 910 (0.15 x 35.9)
Mixture ratio 50 : 1 (2%)
Petrol Minimum 89 octane
Two-stroke engine oil ISO-L-EGD (ISO/CD13738), JASO FC/FD
Tank capacity L (U.S.fl .oz.) 0.68 (23.0)
Diameter - Length mm (in) 8.0 - 1588 (0.31 - 62.52)
Housing OD - ID mm (in) 28.0 - 24.0 (1.10 - 0.94)
Main pipe Length mm (in) 1537 (60.5)
Gear tooth Spiral bevel gear
Lubrication
Arbor diameter for blade mm (in) 25.4 (1.0)
Fastener type, size mm Left-hand thread nut, M10 x 1.25 pitch
Cutting rotation Anticlockwise as viewed from top
SERVICE INFORMATION SRM-420ES
SRM-420ES (L) SRM-420ES (U)
1840 (72.4)
355 (14.0) 680 (26.8)
287 (11.3) 510 (20.1)
8.3 (18.2) 8.8 (19.3)
3
(in3) 41.5 (2.53)
CDI (Capacitor discharge ignition) system
Digital magneto
Front : Crescent loop with cushion grip
Rear : Integrated control grip with cushion
Lithium based grease or ECHO XTended Protection
U-handle with integrated
control grip
TM
Lubricant
OD: Outer diameter. ID: Inner diameter. * Without shoulder harness and standard cutter.
** Refer to Operator’s manual.
Page 3
SERVICE INFORMATIONSRM-420ES
1-2 Technical data
Model
Engine
Idling speed r/min 2,800 +/- 400
Wide open throttle speed r/min 9,500 - 10,500* 10,500 - 11,500**
Clutch engagement speed r/min 3,700
Engagement Limit
Compression pressure MPa (kgf/cm
Ignition system with stop holding function
Spark plug gap mm(in) 0.6 - 0.7 (0.024 - 0.028)
Minimum secondary voltage at 1500 r/min kV 22
Primary coil resistance
(Red Probe on stop terminal of module)
Secondary coil resistance Ω 930 - 970
Pole shoe air gaps mm(in) 0.3 - 0.4 (0.012 - 0.016)
Ignition timing at 3,000 r/min °BTDC 12
Carburettor
Venturi Size 12.7 (0.50)
Throttle Bore 14.3 (0.56)
Idle adjust screw initial setting turns in*** 2 1/8
L mixture needle initial setting turns out 2 3/8
H mixture needle initial setting turns out 3
Test Pressure, minimum MPa (kgf/cm
Metering lever height mm(in) 1.65 (0.06) lower than diaphragm seat
†
at 8,000 r/min °BTDC 25
at 10,000 r/min °BTDC 23
r/min Less 3,300 or over 4,300
2
) (psi) 0.92 (9.4) (132)
MΩ 2.4 -2.9
2
) (psi) 0.05 (0.5) (7.0)
SRM-420ES (L) SRM-420ES (U)
3
BTDC: Before top dead centre.
*With Nylon line cutter and shield.
**With 3-tooth blade (255 mm).
*** Set idle adjust screw to the point that its tip just contacts throttle plate before initial setting.
†
If clutch engagement speed is lower than lower service limit speed or higher than uper service limit speed,
replace clutch assembly with new one.
Page 4
4
1-3 Torque limits
Descriptions Size kgf•cm N•m in•lbf
Starter Pawl M 8 60 - 90 6 - 9 50 - 80
system
Ignition Magneto rotor (Flywheel) M 8 200 - 240 20 - 24 175 - 210
system
Spark plug M 14 130 - 170 13 - 17 115 - 150
Fan cover M 5 30 - 45 3 - 4.5 26 - 40
Fuel Carburettor M 5 40 - 55 4 - 5.5 35 - 50
system
Intake insulator M 5 50 - 70 5 - 7 45 - 60
Insulator plate M 5 30 - 45 3 - 4.5 26 - 40
Fuel tank bracket M 5 50 - 70 5 - 7 45 - 60
Fuel tank M 5 50 - 70 5 - 7 45 - 60
Clutch Clutch shoe M 6 70 - 110 7 - 11 60 - 95
Engine Crankcase M 5** 70 - 110 7 - 11 60 - 95
Cylinder M 5** 70 - 110 7 - 11 60 - 95
Cylinder cover M 5 20 - 30 2 - 3 17 - 26
Stand M 5 20 - 30 2 - 3 17 - 26
Muffl er M 6 100 - 140 10 - 14 90 - 125
Muffl er cover M 5* 30 - 45 3 - 4.5 26 - 40
Muffl er stay M 5 60 - 90 6 - 9 50 - 80
Others Blade fastening nut LM 10 280 - 320 28 - 32 245 - 280
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
M 6 45 - 75 4.5 - 7.5 40 - 65
M 8 110 - 150 11 - 15 95 - 130
M 10 210 - 300 21 - 30 180 - 260
Starter case M 5 30 - 45 3 - 4.5 26 - 40
Ignition coil M 5 50 - 70 5 - 7 45 - 60
Intake bellows M 5 30 - 50 3 - 5 26 - 45
SERVICE INFORMATION SRM-420ES
LM: Left hand thread.* Apply thread locking sealant. (See below)
** The torque differences among four bolts should not exceed 20 kgf•cm (2N•m, 17in•lbf) on one cylinder or
crankcase.
1-4 Special repairing materials
Material
Grease Gear case
Rewind spring
Starter center post
Oil Oil seal inner lips
Drive shaft
Thread locking sealant Muffl er cover Loctite #242, ThreeBond #1324 or equivalent
Location
Lithium based grease or ECHO XTended Protection
Lubricant
Two-stroke engine oil or engine oil (SAE#30)
Remarks
TM
Page 5
SERVICE INFORMATIONSRM-420ES
5K225 5K016 5K042
5K1895K219 5K220
5K246
5K245
5K223 5K2245K222
1-5 Service limits
ABCD
EFGH
5
KLM
Description
A Cylinder bore When plating is worn and aluminum can be seen
B
Piston outer diameter Min. 39. 91 (1.571)
C
Piston pin bore Max. 10. 035 (0.3951)
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. 9. 98 (0.3929)
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. 13. 025 (0.5128)
L
Crankshaft runout Max. 0. 02 (0.001)
M
Clutch drum bore Max. 71. 5 (2.81)
mm (in)
Page 6
6
1-6 Special tools
1
2: b
SERVICE INFORMATION SRM-420ES
= 6
mm
3
54
6
PET-304
1.3
1.65
0.4
1.5
b
mm
= 80
a
7
8:
9:
a
= 70
mm
10
a
21
a
16
17
b
23
24
12
19
13
20
= 12
a
14:
= 32
b
= 15
: a
15
= 24.5
b
mm
mm
mm
mm
22
Key Part Number Description Used for:
1 G310-000050
Tachometer PET-304
Measuring engine speed to adjust carburettor
2 X605-000050 Torx L wrench Removing and installing bolt
3 897501-03938 Puller Removing fl ywheel
4 897835-16131 Pressure connector Testing crankcase and cylinder leakages
5 897537-30130 Piston stopper Locking crankshaft rotation
6 897563-19830 Metering lever gauge Measuring metering lever height on carburettor
7 897603-23030 PTO shaft puller Removing PTO shaft
8 897701-02830 Bearing wedge Removing ball bearing remaining on crankshaft
9 897701-06030 Bearing wedge Removing ball bearing on PTO shaft / drive gear
10 897701-14732 Bearing tool
Removing and installing ball bearings on crankcase / clutch drum
11 897702-30131 Piston pin tool Removing and installing piston pin (Use 10mm dia. adapter)
12 897712-04630 2-pin wrench Removing and installing pawl carrier
13 897714-12330 Oil seal tool Installing crankcase oil seal (clutch side)
14 897714-24330 Oil seal tool
Installing crankcase oil seal (starter side) / PTO shaft bearings
15 897726-21430 Oil seal tool Installing crankcase oil seal (clutch side)
16 897718-03930 Bearing tool Installing crankcase oil seal (starter side)
17 897719-02830 Piston holder Making piston steady to remove and install piston / ring
18 363018-00310 Washer Installing crankcase oil seal (starter side)
19 897800-79931 Spark tester Checking ignition system
20 897803-30132 Pressure tester Testing fuel pipes/tank and crankcase leakages
21 897826-16131 Pressure plug Plugging intake port to test crankcase / cylinder sealing
22 897827-16131 Pressure plate Plugging intake port to test crankcase / cylinder sealing
23 897831-16131 Pressure plug Plugging exhaust port to test crankcase / cylinder sealing
24 91037 Compression gauge Measuring cylinder compression
25 Y089-000091 D-shaped tool Adjusting mixture needle
11
18
50
0.4
0
0
MPa
1.
25
0.8
1.2
7
1
4
2
3
Page 7
SERVICE INFORMATIONSRM-420ES
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.
The fuel is fresh ( > 89 octane : RON ) and properly mixed at 50 : 1 with “ISO L-EGD” or “JASO FC/FD” 2-stroke oil.
5.
6. Install nylon line cutter with 2 nylon lines with 150 mm, even if 3-tooth blade is installed, for proper engine loading to make sure engine speed on both SRM-420ES(L) and SRM-420ES(U).
B. Preliminary adjustment. Adjustment by Idle adjust screw of carburetor.
Start and run engine for 3 minute
onds.
Adjust idle engine speed to 2,800 +/- 100 r/min by turning Idle adjust screw. Confi rm WOT engine speed
approx. 10,000 r/min. If engine does not run correctly after this adjustment, proceed to the next step 2-2.
2-2 Presetting Idle adjust screw, L mixture needle and H mixture needle
(B)
alternating engine speed between WOT for 50 seconds and idle for 10 sec-
Tools Required : Small screwdriver with 2.5 mm
blade, P/N G310-000050 electronic tachometer,
(D)
(C)
P/N Y089-000091 D-shaped tool (A).
1. Turn L and H mixture needle clockwise until
lightly seated, and then turn out both mixture needles following turns.
7
(A)
L mixture needle (B) : 2 3/8
H mixture needle (C) : 3
NOTE :
ing, damage to carburettor may occur.
2. Remove air cleaner lid to expose the Idle adjust
screw and throttle plate. Turn Idle adjust screw (D)
anticlockwise until Idle adjust screw tip just touches throttle plate. Then turn it clockwise 2 1/8 turns.
Reinstall air cleaner lid.
NOTE :
just screw, Idle and H mixture needles are intended
to start and run the engine before fi nal carburettor
adjustments are made through this procedure. The
actual number of turns needed for engine operation may vary.
If needles are overtighented during seat-
The initial carburettor settings for Idle ad-
Page 8
8
2-3 Adjusting carburettor
(D)
(B)
(C)
SERVICE INFORMATION SRM-420ES
SRM-420ES(L): Remove shield and cut trimmer
head line lengths to 190 mm.
SRM-420ES(U) : Remove shield and blade, and
cut trimmer head line lengths to 190 mm.
1. Start and warm engine for 3 minute alternating
engine speed between WOT for 50 seconds and
idle for 10 seconds.
2. Adjust L mixture needle (B) to reach maximum
idle speed using 2.5 mm blade screwdriver.
3. Set Idle speed to 3,550 r/min by turning Idle
adjust screw (D). Engine speed should be stable at
3,550 +/- 50 r/min.
4. Turn L mixture needle (B) anticlockwise to reduce engine idle speed 800 r/min to set idle speed
at 2,750 r/min. The idle speed range is 2,650 - 2,850
r/min.
5. Turn Idle adjust screw (D) clockwise to increase
idle engine speed to set idle at 2,800 r/min. The
idle speed range is 2,700 to 2,900 r/min.
t = 190 mm
NOTE :
a minimum of 20 seconds after each adjustment of
idle mixture needle to assure accurate tachometer
readings.
6. Adjust H mixture needle (C) to reach maximum
WOT engine speed. Then turn H mixture needle (C)
anticlockwise to reduce WOT engine speed 120
r/min (RANG : 100-140 r/min).
max. approx. 9,000 r/min
NOTE :
out shield.
7. SRM-420ES(L) : Stop engine, and restart engine and verify engine idle speed ranges from 2,400
to 3,200 r/min, and expand and cut nylon line by
shield knife and WOT engine speed ranges from
9,500 to 10,500 r/min.
NOTE :
shield
SRM-420ES(U) : Stop engine and reinstall shield
for 3-tooth blade (255 mm) and the blade. Restart
engine and verify engine idle speed ranges from
2,400 to 3,200 r/min, and WOT engine speed
ranges from 10,500 to 11,500 r/min.
Make sure the nylon line cutter does not rotate
when engine is at idle. Engine should start and accelerate smoothly.
Engine speed must be allowed to stabilize
Nylon line length should be 190 mm with-
Nylon line length should be 150 mm with
NOTE :
may vary from fi nal adjustment specifi cations due
to changing ambient conditions, fuel, and engine
loads. Safe engine speed variances should be
within the WOT and Idle speed ranges listed in
Section 1-2, otherwise the carburettor should be
readjusted.
WOT, and idle speed in field operation
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