Troy-Bilt TB90BC - Manual (Page 21)

MAINTENANCE AND REPAIR INSTRUCTIONS
21
Fig. 43
CARBURETOR ADJUSTMENT
The idle speed of the engine is adjustable through the
Air Filter/Muffler cover (Fig. 43).
NOTE: Careless adjustments can seriously damage your
unit. An authorized service dealer should make
carburetor adjustments.
Check Fuel Mixture
Old and/or improperly mixed fuel is usually the reason for
the unit not running properly. Drain and refill the tank with
fresh, properly mixed fuel prior to making any adjustments.
Refer to Oil and Fuel Information Pg. 12.
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 Pg. 19.
Adjust Idle Speed Screw
WARNING: The cutting attachment may be
spinning during idle speed adjustments.
Wear protective clothing and observe all
safety instructions to prevent serious
personal injury.
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 5
minutes to warm up. See Starting/Stopping
Instructions, Pg. 13.
2. Release the throttle trigger and let the engine idle. If
the engine stops, insert a small phillips or flat blade
screwdriver into the hole in the air filter/muffler cover
(Fig. 43). 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.
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 screw should solve most engine
problems.
If not and:
• 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.
WARNING: When the unit is turned off
make sure the cutting attachment has
stopped before the unit is set down to
prevent serious personal injury.
Idle Speed Screw