Troy-Bilt TB590BC Manuel De L'opérateur page 14

Adjust Idle Speed Screw
If, after checking the fuel 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 in between the Air Filter
Cover and the Engine Cover (Fig. 51). 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, 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.
ROCKER ARM CLEARANCE
This requires disassembly of the engine. If you feel unsure or
unqualified to perform this, take the unit to an authorized
service center.
NOTE: Inspect the valve to rocker arm clearance with a feeler
gauge after the first 10 hours of operation and every 25
hours of operation.
• The engine must be cold when checking or adjusting the
valve clearance.
• This task should be performed inside, in a clean, dust free
area.
1. Remove the six (6) screws on the back of the engine cover
with a Flat-head or T-25 Torx screwdriver (Fig. 52).
View Of The Rear Engine Cover
Remove
Screws
2. Disconnect the spark plug wire.
3. Clean dirt from around the spark plug. Remove the spark
plug from the cylinder head by turning a 5/8 in. socket
counterclockwise.
4. Remove the engine cover (Fig. 52).
5. Clean dirt from around the rocker arm cover. Remove the
screw holding the rocker arm cover with a large flat blade
screwdriver or Torx T-25 bit (Fig. 53). Remove the rocker
arm cover and gasket.
6. Pull the starter rope slowly to bring the piston to the top of its
travel, (known as top dead center). Check that:
MAINTENANCE AND REPAIR INSTRUCTIONS
Remove
Screws
Fig. 52
• The piston is at the top of its
travel while looking in the
spark plug hole (Fig. 54)
• Both rocker arms move
freely, and both valves are
closed
If these statements are not true,
repeat this step.
7. Slide the feeler gauge
between the rocker arm and
the valve return spring.
Measure the clearance
between the valve stem and
rocker arm (Fig. 54). Measure
both the intake and exhaust
valves.
Rocker Arms
Feeler Gauge
Spark Plug
Hole
The recommended clearance for both intake and exhaust is
.003 – .006 in. (.076 – 0.152 mm). Use a standard automotive
.005 in. (0.127 mm) feeler gauge. The feeler gauge should slide
between the rocker arm and valve stem with a slight amount of
resistance, without binding. See Figures 54 and 55.
Adjusting Nut
.003–.006 in.
(.076–.152 mm)
8. If the clearance is not within specification:
a. Turn the adjusting nut using a 5/16 inch (8 mm) wrench or
nut driver (Fig. 54).
• To increase clearance, turn the adjusting nut
counterclockwise.
• To decrease clearance, turn the adjusting nut clockwise.
14
Rocker
Arm
Cover
Spark
Plug
Hole
Fig. 53
Adjusting Nuts
INTAKE
EXHAUST
Fig. 54
Rocker Arm
Feeler Gauge
Valve Stem
Fig. 55