SERVICE INFORMATION
SRM-420ES
3
1-2 Technical data
Model
SRM-420ES (L)
SRM-420ES (U)
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
†
r/min
Less 3,300 or over 4,300
Compression pressure
MPa (kgf/cm
2
) (psi)
0.92 (9.4) (132)
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
M
Ω
2.4 -2.9
(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
at 8,000 r/min
°BTDC
25
at 10,000 r/min
°BTDC
23
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
2
) (psi)
0.05 (0.5) (7.0)
Metering lever height
mm(in)
1.65 (0.06) lower than diaphragm seat
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.
