McCulloch MT780 - Manual (Page 19)

19
MAINTENANCE AND REPAIR INSTRUCTIONS
Fig. 39
Idle Speed
Screw
3. If the cutting attachment rotates when the engine
idles, turn the idle speed screw counterclockwise
1/8 of a turn at a time (as needed), to reduce idle
speed.
Checking the fuel mixture, cleaning the air filter, and
adjusting the idle speed should solve most engine
problems.
If not and all of the following are true:
• The engine will not idle
• The engine hesitates or stalls on acceleration
• There is a loss of engine power
Have the carburetor adjusted by an authorized service
dealer.
Check Fuel Mixture
Old and/or improperly mixed fuel is usually the reason
for improper unit performance. Drain and refill the tank
with fresh, properly-mixed fuel prior to making any
adjustments. Refer to Oil and Fuel Information.
Clean Air Filter
The condition of the air filter is important to the operation
of the unit. A dirty air filter will restrict air flow and
change the air/fuel mixture. This is often mistaken for an
out of adjustment carburetor. Check the condition of the
air filter before adjusting the idle speed screw. Refer to
Air Filter Maintenance.
Adjust Idle Speed Screw
If, after checking the fuel mixture and cleaning the air
filter, the engine still will not idle, adjust the idle speed
screw as follows:
1. Start the engine and let it run at a high idle for a
minute to warm up. Refer to Starting/Stopping
Instructions.
2. Release the throttle trigger and let the engine idle. If
the engine stops, insert a small phillips screwdriver
into the hole in the air filter/muffler cover (Fig. 39).
Turn the idle speed screw in, clockwise, 1/8 of a
turn at a time (as needed) until the engine idles
smoothly.
NOTE: The cutting attachment should not rotate when
the engine idles.
CARBURETOR ADJUSTMENT
The idle speed of the engine is adjustable through the air
filter/muffler cover (Fig. 39).
NOTE: Careless adjustments can seriously damage your
unit. An authorized service dealer should make
carburetor adjustments.
The cutting
attachment may spin
during idle speed adjustments. Wear
protective clothing and observe all safety
instructions to prevent serious personal injury.
WARNING:
To prevent serious
personal injury,
make sure the cutting attachment has
stopped rotating before you turn it off and
set it down.
WARNING: