Service Manual

NOTE: Follow these carburetor adjustment proce-
dures carefully. An incorrectly adjusted carburetor can
cause severe engine damage.
Make sure the unit is fully assembled before making
carburetor adjustments:
For trimmers and brush cutters, make sure the boom,
cutting head, and line guard are installed and the cut-
ting line is extended to its full cutting length.
For cultivators, make sure the boom and gear box are
installed.
For blowers and blower-vacs, make sure the blower
tube and nozzle are installed.
The carburetor has three basic adjustments: the idle
speed adjustment, the idle mixture adjustment, and
the high speed mixture adjustment (Figure 1-12).
Figure 1-12. Carburetor Adjustments.
1. Remove air filter cover assembly as instructed in
Part 3 — Engine Disassembly.
2. Initial Idle Speed Setting: Turn idle speed screw
counterclockwise until it does not touch the throttle
lever. Now turn the screw clockwise until it just
touches the throttle lever; then continue turning 2
full turns.
3. If so equipped, remove the rubber cap from the high
speed mixture adjustment needle.
4. Initial High Speed Mixture and Idle Mixture Settings:
Turn both the high speed mixture and idle mixture
needles clockwise until they are lightly seated.
Then turn the needles counterclockwise the follow-
ing number of turns:
High Speed Mixture Needle: 1-1/4 turns
Idle Mixture Needle: 1-1/4 turns
NOTE: Turn the high speed mixture and idle mix-
ture needles finger-tight. Do not force the needles
with a screwdriver as this can damage the tips of
the needles and the seats in the carburetor body.
5. Start engine and allow it to warm up for 3 to 5 min-
utes.
NOTE: For the following steps, use a magnetic
pick-up 2-cycle engine tachometer to monitor en-
gine speed.
6. Final High Speed Mixture Setting: Squeeze the throt-
tle trigger to the FULL (WIDE OPEN) THROTTLE
position. Turn the high speed mixture needle clock-
wise or counterclockwise to set the high speed
RPM:
Trimmers and Cultivators: 6,800 to 7,200 RPM
Blowers and Blower-Vacs: 6,600 to 7,200 RPM
7. Release the throttle trigger and let the engine idle. If
the engine stops, turn the idle speed screw clock-
wise 1/8 turn at a time until the engine idles.
8. Final Idle Mixture and Idle Speed Settings: Adjust
the the idle mixture and idle speed as follows:
a. Turn the idle mixture needle clockwise until the
fastest idle RPM is reached; then turn the nee-
dle counterclockwise 1/8 turn.
b. Squeeze the throttle trigger. If the engine falters
or hesitates as it accelerates, turn the idle mix-
ture needle counterclockwise 1/16 turn at a
time until the engine accelerates rapidly.
(L) Idle
Mixture Needle
(H) High Speed
Mixture Needle
Idle Speed
3.6081.012
1
GENERAL INFORMATION
1-13