Maintenance And Repair Instructions; Replacing The Spark Plug - Troy-Bilt TB539E Operator's Manual

4-cycle gas trimmer

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Pull the starter rope slowly to bring the piston to the top of

its travel, (known as top dead center). Check that:

• The piston is at the top of its travel while looking in the

spark plug hole (Fig. 37).

• Both rocker arms move freely, and both valves are closed.

If these statements are not true, repeat this step.

Slide the feeler gauge between the rocker arm and the

valve return spring. Measure the clearance between the

valve stem and rocker arm (Fig. 38). Measure both the

intake and exhaust valves.

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 38 and 39.

If the clearance is not within specification:

a. Turn the adjusting nut using a 5/16 inch (8 mm) wrench or nut driver (Fig. 39).

• To increase clearance, turn the adjusting nut counterclockwise.

• To decrease clearance, turn the adjusting nut clockwise.

b. Recheck both clearances, and adjust as necessary.

Reinstall the rocker arm cover using a new gasket. Torque

the screw to 20–30 in•lb (2.2–3.4 N•m).

10.

Check the spark plug and reinstall. See Replacing the

Spark Plug.

11.

Replace the spark plug wire.

12.

Reinstall the engine cover. Check alignment of the cover

before tightening the screws. Tighten screws.

REPLACING THE SPARK PLUG

Use a replacement part number 753-05255 spark plug. The

correct air gap is 0.025 in. (0.635 mm.). Remove the plug after

every 25 hours of operation and check its condition.

Stop the engine and allow it to cool. Remove the six (6) screws on the back of the engine cover

with a Flat-head or T-25 Torx screwdriver (Fig. 40).

Grasp the plug wire firmly and pull the cap from the spark plug.

Clean dirt from around the spark plug. Remove the spark plug from the cylinder head by turning a

5/8 in. socket counterclockwise.

WARNING:

Do not sand blast, scrape or clean electrodes. Grit in the engine could

damage the cylinder.

Replace cracked, fouled or dirty spark plug. Set the air gap at 0.025 in. (0.635 mm.) using a feeler

gauge (Fig. 40).

Install a correctly-gapped spark plug in the cylinder head. Turn the 5/8 in. socket clockwise until

snug.

If using a torque wrench torque to:

110-120 in.•lb. (12.3-13.5 N•m)

Do not over tighten.

SPARK ARRESTOR MAINTENANCE

Remove the rear engine cover. See Rocker Arm Clearance.

With a flat blade screwdriver or Torx T-20 bit and a T-25 bit,

remove the screws attaching the spark arrestor cover to the

muffler (Fig. 41).

Pull the tab on the spark arrestor cover out of the muffler.

Remove the spark arrestor cover.

Remove the spark arrestor screen from the spark arrestor cover.

Clean the spark arrestor screen with a wire brush or replace it.

Reinstall the spark arrestor screen, spark arrestor cover and screws.

CLEANING

WARNING:

To avoid serious personal injury, always turn the unit off and allow it to cool

before you clean or service it.

Use a small brush to clean off the outside of the unit. Do not use strong detergents. Household cleaners

that contain aromatic oils such as pine and lemon, and solvents such as kerosene, can damage plastic

housing or handle. Wipe off any moisture with a soft cloth.

STORAGE

• Never store the unit with fuel in the tank where fumes may reach an open flame or spark.

• Allow the engine to cool before storing.

• Lock up the unit to prevent unauthorized use or damage.

• Store the unit in a dry, well-ventilated area.

• Store the unit out of the reach of children.

LONG TERM STORAGE

Drain all gasoline from the gas tank into a container. Do not use gas that has been stored for more

than 60 days. Dispose of the old gasoline in accordance to Federal, State, and Local regulations.

Start the engine and allow it to run until it stalls. This ensures that all gasoline has been drained

from the carburetor.

Allow the engine to cool. Remove the spark plug and put 5 drops of high quality motor oil into the

cylinder. Pull the starter rope slowly to distribute the oil. Reinstall the spark plug.

NOTE:

Remove the spark plug and drain all of the oil from the cylinder before attempting to start the

trimmer after storage.

Change the oil, referring to Changing the Oil. Dispose of the old oil in accordance to Federal, State

and Local regulations.

Thoroughly clean the unit and inspect for any loose or damaged parts. Repair or replace damaged

parts and tighten loose screws, nuts or bolts. The unit is ready for storage.

TRANSPORTING

• Allow the engine to cool before transporting.

• Secure the unit while transporting.

• Drain the gas tank before transporting.

• Tighten gas cap before transporting.