Troy-Bilt TB525 EC Replacing the Spark Plug, NOTE:, in•lb, reduce idle speed, clean or service it, Do not over tighten, clockwise until snug, ROCKER ARM CLEARANCE

MAINTENANCE AND REPAIR INSTRUCTIONS

AIR FILTER MAINTENANCE		Air Filter
WARNING: To avoid serious		Cover
personal injury, always turn the unit		Air Filter
off and allow it to cool before you
clean or service it.
Cleaning the Air Filter		Tab
		Fig. 29
Failure to maintain your air filter properly can
result in poor performance or can cause	Back
permanent damage to your engine.
	Plate
1. Open the air filter cover. Push the tab on the
		Tabs
under side of the cover inward. Then pull the
air filter cover out and up. (Fig. 29).
2. Remove the air filter (Fig. 30).	Air	Locking
3. Wash the filter in detergent and water. Rinse
	Filter	Tab
the filter thoroughly and allow it to dry.		Fig. 30
4. Apply enough clean SAE 30 motor oil to
lightly coat the filter.

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. 32).

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. 33). 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:

•The piston is at the top of its travel while looking in the spark plug hole (Fig. 33).

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

If these statements are not true, repeat this step.

		Adjustment
	Intake	Nuts
Rocker
Arms
		Exhaust
	Fig. 34
Adjusting		Rocker Arm
Nut		Feeler
		Gauge
0.003–0.006 in.
(0.076–0.152 mm)
		Valve Stem
	Fig. 35

5.	Squeeze the filter to spread and remove excess oil.
6.	Replace the filter (Fig. 30).
NOTE: If the unit is operated without the air filter, you will VOID the		.

7.Reinstall the air filter cover. Position the slots on the top of the air filter cover onto the tabs at the top of the back plate (Fig. 29).

8.Swing the cover down until the tab on the air filter backplate snaps into place in the slot on the air filter cover (Fig. 29).

IDLE SPEED ADJUSTMENT

The idle speed of the engine is adjustable. An idle adjustment screw is between the air filter cover and the engine starter housing (Fig. 31).

NOTE: Careless adjustments can seriously damage your unit. An authorized service dealer should make carburetor adjustments.

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. 34). 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 (Fig. 34 and 35).

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. 35).

•To increase clearance, turn the adjusting nut counterclockwise.

•To decrease clearance, turn the adjusting nut clockwise.

b. Recheck both clearances, and adjust as necessary.

WARNING: The cutting attachment may spin during idle speed adjustments. Wear protective clothing and observe all safety instructions to prevent serious personal injury.

If, after checking the fuel and cleaning the air filter, the engine still will not idle, adjust the idle speed screw as follows:

Idle Adjustment Screw

Fig. 31

9.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 753-05784 or Champion® RDZ4H spark plug. The correct air gap is 0.025 in. (0.635 mm.).

1.Start the engine and let it run at a high idle for a minute to warm up. Refer to Starting and 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. 31). 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

1.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. 36).

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

3.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.

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.

4.	Replace cracked, fouled or dirty spark plug.
	Set the air gap at 0.025 in. (0.635 mm.)
	using a feeler gauge (Fig. 36).
5.	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)

0.025 in.

(0.635 mm)

ROCKER ARM CLEARANCE

WARNING: To avoid serious personal injury, always turn the unit off and allow it to cool before you clean or service it.

This adjustment requires disassembly of the engine. If you feel unsure or unqualified to perform this, take the unit to an authorized service center.

•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. 32).

View Of The Rear Engine Cover

ScrewsScrews

Fig. 32

Rocker Arm

Cover

Spark Plug

Hole

Fig. 33

Do not over tighten.

Fig. 36

9