Echo CS-4510-18 Operator's Manual page 27

Idle adjusting screw
Low mix needle (L)
High Altitude Operation
This engine has been factory adjusted to maintain
satisfactory starting, and durability performance
up to 330 m / 1,100 ft above sea level (ASL) (96.0
kPa).
To maintain proper engine operation and above
330 m / 1,100 ft ASL the carburetor may need to be
adjusted by an authorized ECHO service dealer.
IMPORTANT
If the engine is adjusted for operation above
330 m / 1,100 ft ASL, the carburetor must be
readjusted when operating the engine below
330 m / 1,100 ft ASL, otherwise severe engine
damage may result.
High mix needle (H)
27
CARBURETOR ADJUSTMENT
Every unit is run at the factory and the carburetor is
set in compliance with Emission Regulations.
In addition, the carburetor is equipped with "H" (High
Mix) and "L" (Low Mix) needle adjustment
limiters that prevent settings outside acceptable
limits.
1. Before adjusting carburetor clean or replace air
filter and muffler "Spark Arrestor Screen".
2. Make sure the bar and chain are properly
adjusted.
3. Start engine and run several minutes to bring to
operating temperature.
Flash choke twice during warm-up to clear any
air from the fuel system.
4. Stop engine.
Gently turn "H" mix needle counterclockwise
(CCW) to stop.
Gently turn "L" mix needle midway between full
clockwise (CW) stop and CCW stop.
5. Idle Speed Adjustment:
• Start engine, turn "Idle" speed adjustment
screw CW until the saw chain begins to move,
then turn screw out CCW until the saw chain
stops moving.
Turn screw out, CCW, an additional ½ turn.
WARNING
Cutting attachment must not move when unit
is idling.
6. Accelerate to full throttle for 2 - 3 seconds to
clear any excess fuel in the engine, then return
to idle.
Accelerate engine to full throttle to check for
smooth transition from idle to high speed.
If engine hesitates turn "L" needle CCW 1/8 turn
and repeat acceleration.
Continue adjustment until smooth acceleration
results.
7. Check idle speed and reset if necessary as
described in item 5.
If a tachometer is available idle speed should be
set to 3,100 r/min.
CAUTION
When starting, idling adjustment speed
should be adjusted not to rotate the saw
chain.
Correct idle speed is adjusted 3100 r/min.
Or ½ turn CCW from the point the chain
stops moving.
When you experience trouble with the
carburetor, contact your dealer.
CS-4510