Echo SRM-420ES (L): SRM-420ES (U) Service Data
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
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.
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.
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