Cub Cadet HB425 WARNING:, CAUTION:, WARNING:, WARNING:, SPECIFICATIONS, MAINTENANCE AND REPAIR INSTRUCTIONS, N•m), N•m), NOTE:, NOTE:, NOTE:, NOTE:, NOTE:, 20

MAINTENANCE AND REPAIR INSTRUCTIONS

7. Reinstall the air filter	Back	Back Plate Slots
cover. Position the	Plate Slot
hooks on the right
side of the air filter
cover into the slots
at the right side of
the back plate (Fig.
25).
8. Swing the cover to
the left until the tab
on the air filter cover
snaps into place in
the slot on the back		Fig. 25
plate (Fig. 26).

CARBURETOR ADJUSTMENT

WARNING: This unit will need to be running during idle speed adjustment. Wear protective clothing and observe all safety instructions to prevent serious personal injury.

Also, DO NOT set unit on any surface except a clean, hard area while starting or performing any adjustments. Debris, such as gravel, sand, dust, grass, etc., could be thrown by the blower tube and damage property or cause serious injury to bystanders or operator.

The idle speed of the engine is adjustable. An idle adjustment screw is between the air filter cover and the engine starter housing (Fig. 27). NOTE: Careless adjustments can seriously damage your unit. An

authorized service dealer should make carburetor adjustments.

Check Fuel

Old fuel is usually the reason for improper unit performance. Drain and refill the tank with fresh 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. 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 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. 27). Turn the idle speed screw in, clockwise, 1/8 of a turn at a time (as needed) until the engine idles smoothly.

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.

Crochet

Air Filter	Air Filter Cover
	Fig. 26
	Fig. 26

Idle Adjustment

Screw

	Fig. 27
Muffler	Starter Housing
Cover	Screws (2)
		Starter
	Starter	Housing
	Housing	Screws
		(4)

Fig. 28

NOTE: Make sure that the screws are reinstalled into their original holes (Fig. 28).

REPLACING THE SPARK PLUG

CAUTION: Do not sand blast, scrape, or clean electrodes. Grit in the engine could damage the cylinder.

Use a replacement part number 753-05784. The correct spark gap is

0.025 in. (0.635 mm.). Remove the plug after every 40 hours of 0.025 in. (0.635 mm)

operation and check its condition.

1. Stop the engine and allow it to cool.

2. Remove the 2 plastic muffler cover screws with a flat blade or T-25 Torx head screwdriver (Fig. 28), then remove the cover.

3.Remove the 2 plastic and 4 aluminum starter housing screws

with flat blade or T-25 Torx head screwdriver (Fig. 28), then
		Fig. 32
remove the housing.		Fig. 32

NOTE: Make sure to store the screws so that they can be reinstalled into their original holes.

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

5.Clean dirt from around the spark plug. Remove the spark plug from the cylinder head by turning a 5/8 in. socket counterclockwise.

6.Replace cracked, fouled or dirty spark plug. Set the spark gap at 0.025 in. (0.635 mm.) using a feeler gauge (Fig. 32).

7.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			Muffler
	WARNING: To avoid serious personal injury,
	always turn your unit off and allow it to cool		Spark Arrestor
	before you clean or do any maintenance on it.		Cover
1.	Remove the muffler cover. See Rocker Arm Clearance.		T-25
1.	Remove the muffler cover. See Rocker Arm Clearance.		Screw
2.	With a flat blade screwdriver or Torx T-20 bit and a T-25 bit,
	remove the screws attaching the spark arrestor diverter to the
	muffler (Fig. 33).
3.	Remove the spark arrestor cover.	Spark Arrestor
4.	Remove the spark arrestor screen from the spark arrestor cover.	Spark Arrestor	T-20 Screw
5.	Clean the spark arrestor screen with a wire brush or replace it.	Screen	T-20 Screw
5.			Fig. 33
6.	Reinstall the spark arrestor screen, spark arrestor cover, and		Fig. 33
	screws.

7.Reinstall the muffler cover.

CLEANING

WARNING: To avoid serious personal injury, always turn your unit off and allow it to cool before you clean or do any maintenance on 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.

ROCKER ARM CLEARANCE

This requires disassembly of the engine. If you feel unsure or unqualified to perform this, take the unit to a qualified service dealer. NOTE: Inspect the valve to rocker arm clearance with a feeler

gauge after the first 10 hours of operation and every 40 hours of operation.

Rocker Arm

• Store the unit out of the reach of children.

LONG TERM STORAGE

1.	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.
2.	Start the engine and allow it to run until it stalls. This ensures that all gasoline has been drained from
	the carburetor.

•The engine must be cold when checking or adjusting the rocker arm clearance.

•This task should be performed inside, in a clean, dust free area.

1.Remove the 2 muffler cover screws with a flat blade or T-25 Torx head screwdriver (Fig. 28), then remove the cover.

2.Remove the 6 starter housing screws with flat blade or T-25 Torx head screwdriver (Fig. 28), then remove the housing.

NOTE: Make sure to store the screws so that they can be reinstalled into their original holes.

Spark Plug

Hole

Cover

3. 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 blower after storage.

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

5.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

3.Disconnect the spark plug wire.

4.Clean dirt from around the spark plug. Remove the spark plug from the cylinder head by turning a 5/8 in. socket counterclockwise.

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. 29). Remove the rocker arm cover and gasket.

6. Turn the flywheel 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. 29)

•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. 30 & 31). Measure both the intake and exhaust valves.

Fig. 29

		Adjusting
		Nuts
	INTAKE	O-Ring
	Rocker Arms	O-Ring
	Rocker Arms
		EXHAUST
	Feeler Gauge
	Fig. 30

•Allow the engine to cool before transporting.

•Secure the unit while transporting.

•Drain the gas tank before transporting.

•Tighten gas cap before transporting.

SPECIFICATIONSENGINE*

Engine Type . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Air-Cooled, 4-Cycle Displacement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.5 cu. in. (25 cc) Blower Operating RPM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7,000 rpm Idle Speed RPM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3,200 – 4,400 rpm

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 30 and 31.

Ignition Type . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Electronic Ignition Switch . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Momentary Switch Valve clearance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.003–0.006 in. (0.076–0.152 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. 31).

•To increase clearance, turn the adjusting nut counterclockwise.

•To decrease clearance, turn the adjusting nut clockwise.

b. Recheck both clearances, and adjust as necessary.

9.Reinstall the rocker arm cover using a new gasket (Fig. 29). 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.Reinstall the spark plug wire.

12.Reinstall the engine cover. Check alignment of the cover before tightening the screws. Tighten screws.

Adjusting

Nut

.003–.006 in

(0.076–

0.152 mm)

Culbuteur

Feeler

Gauge

Valve Stem

Fig. 31

Spark Plug . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Champion Spark Plug #RDZ4H or Similar Spark Plug Spark Plug Gap . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.025 inch (0.635 mm) Lubrication. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . SAE 30 Oil Crankcase Oil Capacity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.03 oz (60 ml) Fuel. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Unleaded Carburetor. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Diaphragm, All-Position Starter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Auto Rewind Muffler. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Baffled with Guard Throttle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Variable Speed Fuel Tank Capacity. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 oz (414 ml)

*All specifications are based on the latest product information available at the time of printing. We reserve the right to make changes at any time without notice.