Echo CS-420ES - Manual (Page 9)

SERVICE INFORMATION CS-420ES
9
2-3 Adjusting carburettor
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 sec-
onds for another minute and a half.
NOTE : Do not run engine at high speed without
load longer than 10 seconds, or engine damage
may occur.
3. Adjust L mixture needle to reach maximum en-
gine rpm just before lean drop off.
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 : Engine speed must be allowed to stabilize a minimum of 20 seconds after each adjustment of L
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.
7. After adjusting carburettor, screw new lim-
iter 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)
NOTE : Align the limiter cap’s tabs (A) with locat-
ing slots (B) in extended housing of carburettor.
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 : The initial carburettor settings for idle adjust screw, L and H mixture needles are intended to start
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.
NOTE : Engine WOT, and idle engine speed in fi eld operation may vary from fi nal adjustment specifi ca-
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 read-
justed.
H mixture needle L mixture needle
Idle adjust screw
H
L
A
B
B
A
C