Echo CS-310, Service Manual

Page: 33 / 75

FUEL SYSTEM
CS-310
31
4-7 Adjusting carburetor (continued)
4-7-3 Adjusting carburetor
1. Start and warm engine for 1 minute alternat-
ing engine speed between WOT and idle every 5
seconds. Turn H mixture needle counterclockwise
until engine speed drops to approx. 12,500 rpm at
WOT.
NOTE : Do not run engine at high speed without
load longer than 10 seconds, or engine damage
may occur.
2. Adjust L mixture needle using 2.5mm blade
screwdriver to reach maximum engine rpm just be-
fore lean rpm drop off.
3. Set idle speed to 3,700 rpm by turning Idle
adjust screw. Engine rpm should be stable at 3,700
+/- 50 rpm after idle adjust screw adjustment.
4. Turn L mixture needle counterclockwise reducing engine idle speed 500 rpm to set idle speed at 3,200
rpm. The idle speed range is 3,100 - 3,300 rpm.
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.
5. Before adjustment, WOT engine speed should be less than or equal to 12,500 rpm. If rpm is higher,
turn H mixture needle counterclockwise until 12,500 rpm is achieved. To make the
fi nal WOT engine
speed adjustment, turn the H mixture needle clockwise in 1/8 turn increments with the engine at idle. Af-
ter each adjustment, accelerate to WOT, and check rpm. The
fi nal rpm should fall within 12,750 - 12,950
rpm.
6. After adjusting carburetor, screw new limiter
cap counterclockwise on the limiter cap removal
tool (C) (P/N 89801) approx. 2 turns as shown, and
put the limiter caps on L and H mixture needles
respectively. Then gently press the caps onto L
and H mixture needles (do not rock caps back and
forth).
NOTE : Align the limiter cap’s tabs (A) with locat-
ing slots (B) in extended housing of carburetor.
IMPORTANT : The limiter caps must be properly installed on L and H mixture needles to comply
with Emission Regulations.
7. Start engine, and verify engine idle speed ranges from 2,800 to 3,600 rpm, and WOT engine speed
ranges from 12,000 to 13,000 rpm. 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 speci fi -
cations.
NOTE : The initial carburetor settings for Idle adjust screw, Idle and Hi speed mixture needles are intend-
ed to start and run the engine before fi nal carburetor adjustments are made to conform the unit to meet
Emission Regulations. The actual number of turns needed for engine operation may vary.
Idle adjust screw
C
L mixture needle H mixture needle
B
A
B
A