
t
MAINTENANCEAND REPAIR INSTRUCTIONS (Continued)
CARBURETORADJUSTMENT
4. Start the engine and let it runfor a minute.
This unit is equippedwith a diaphragm-type cahuretor that
has been carefully calibrated atthe factory. Inmost cases,
nofurther adjustment will be required.
5.
Releasethe throttle trigger and let the engine idle. If
the engine stops, turn the id!e speed screw (Figs. 28
and29) clockwise 118 turnat a time (as required) until
the engine idles.
The condition of the air filter is important to the operation of
the trimmer. A dirty air filter will restrict the air flow, which
upsets the fuel-air mixture inthe cahuretor. The resulting
symptoms are often mistakenfor an out-of-adjustment
cahuretor. Therefore, checkthecondition of theairfilter
beforeadjusting thecarburetor. Referto Air Filter
Maintenance.
If the following conditions are experienced,
it
may be
necessary toadjust the carburetor:
The engine will not idle
The engine hesitates or stalls on acceleration
-
The loss of engine power that is not corrected by
cleaning the air filter and muffler
The engine operates inan erratic or fuel-rich condition
(indicated by excessive exhaust smoke fromthe
muffler)
NOTE: Careless adjustments can seriously
damage your unit.
Adjusting
the
Carburetor
1. Cleanthe air filter if it is dirty. Referto Air Filter
Maintenance.
2. Make the initial settings with the engine stopped.
These initialsettings should allow you to start and
warm upthe trimmer before making the final
adjustments.
InitialldleSpeed Setting
a) ForWalbro cahuretors: Back the idle speed screw
(Fig.
28
-
page 13) out. counterclockwiseuntil
it
does not contact the carburetor throttle lever. Then
turnthe screw in, clockwise, until
it
just begins to
move the throttle lever; thencontinue turning
2
full
turns.
b) For
Zama
cahuretors: Backthe idle speed screw
(Fig. 29
-
page 13) out, counterclockwise, until
it
does not contact the throttle valve located inside of
the carburetor. This isaccomplished by carefully
watching for the movement of the throttle lever to
stop. Then turnthe screw in, clockwise, until it just
begins to move the throttle lever, then continue
turning 1 1/2turns.
m
NOTE: Turn the high speed and idle
mixture screws finger-tight.
Forcingthe mixture screws with a
screwdriver will damage the screw
tip andthe seat inthe carburetor
body.
6. FinalldleSpeed And Mixture Settings: Adjust the
idle speed and mixture for smothest engine idle.
a. Turn the idle mixture screw (Figs. 28 and 29)
clockwise until you hearthe fastest idle; then
turn the screw counterclockwise1/8 turn.
b. Squeezethe throttle trigger. If the engine
falters or hesitates as
it
accelerates, turnthe
idle rnixture screw (Figs. 28 and 29) counter-
clockwise 1/16 turnat a time until the engine
accelerates rapidly.
c. If the idle speed changes significantly
because of steps a and b. readjust the idle
speed screw (refer to Step 2).
m
NOTE: The Bump Head line spool should not
rotate when the engine idles.
7.
High Speed Screw Mixture Adjustment:
a. High speed mixture screw adjustment is not
recommended without a precision high speed
tachometer.
b. Thefactory presets the high speed mixture screw
at 1-114turns out fromthe closed position. Your
unit should performwell at this setting. If additional
adjustment of the highspeed mixture is required,
contact your local authorized service dealer.
3. InitialHighSpeedandldleMixtureSetting: Turn
boththe high andidle rnixture screws clockwise
(Figs. 28 and 29) untilthey are lightlyseated. Then
turnthe screws counterclockwise
1-114turns.