Cub Cadet BV 428, Operator'S Manual

5

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

• 

The piston is at the top of its travel by 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. 
6.  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). Measure both the intake and exhaust 

valves.

The recommended clearance for both intake and exhaust is 

0.003 – 0.006 in. (0.076 – 0.152 mm). Use a standard automotive 

0.005 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 Figure 30.
7.  If the clearance is not within specification:
a.  Turn the adjusting nut using a 5/16 inch (8 mm) wrench or nut 

driver (Fig. 30).

• 

To increase clearance, turn the adjusting nut 

counterclockwise.

• 

To decrease clearance, turn the adjusting nut clockwise.

b.  Recheck both clearances, and adjust as necessary.
8.  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).

9.  Check the spark plug and reinstall. See Replacing the Spark Plug. 
10. Reinstall the spark plug wire.
11. Reinstall the engine cover. Check alignment of the cover before tightening the screws. Tighten screws.
NOTE:  Make sure that the screws are reinstalled into their 

original holes (Fig. 28). 

REPLACING THE SPARK PLUG
Use a replacement part number 

753-05784 or Champion spark 

plug #RDZ4H. The correct spark gap is 0.025 in. (0.635 mm).
1.  Stop the engine and allow it to cool. 
2.  Open the spark plug cover (Fig. 31).
3.  Grasp the plug wire firmly and pull the cap from the spark plug.
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.  Replace cracked, fouled or dirty spark plug. Set the spark gap 

at 0.025 in. (0.635 mm) using a feeler gauge (Fig. 32). 

6.  Install a correctly-gapped spark plug in the cylinder head. Turn 

the 5/8 in. socket clockwise until snug. 

7.  Reinstall the spark plug cover.
If using a torque wrench, torque to: 

110-120 in.•lb. (12.3-13.5 N•m)
Do not over tighten.

CLEANING AND STORAGE

MAINTENANCE SCHEDULE
Perform these required maintenance procedures at the frequency stated in the table. These 

procedures should also be a part of any seasonal tune-up.
NOTE:  Some maintenance procedures may require special tools or skills such as replacement or 

repair of the emission control devices and system. If unsure about these procedures or tools 

are not available; take the unit to a qualified service dealer. Call 

1-877-282-8684 for more 

information.

NOTE:  Maintenance, replacement, or repair of the emission control devices and system may be 

performed by a qualified service dealer.

NOTE:  Please read the EPA statement that came with the unit for a complete listing of terms and 

coverage for the emissions control devices, such as the spark arrestor, muffler, carburetor, 

etc.

CHECKING THE OIL LEVEL
The importance of checking and maintaining the proper oil level in 

the crankcase cannot be overemphasized. Check oil before each 

use:
1.  Stop the engine and allow oil to drain into the crankcase.
2.  Place the engine on a level surface.
3.  Clean the area around the oil plug before removing it.  Keep 

dirt, grass clippings, and other debris out of the engine. 

4.  Remove the oil plug (Fig. 22).
5.  Look into the oil fill hole (use a flashlight if needed). The oil 

should be just touching the innermost thread (Fig. 21).

6.  If the oil level is not touching the innermost thread on the oil fill 

hole, add a small amount of oil to the oil fill hole and recheck 

(Fig. 21). Repeat this procedure until the oil level reaches the 

innermost thread on the oil fill hole.

NOTE:  Do not overfill the unit.
NOTE:  Make sure the O-ring is in place on the oil plug when 

checking and changing the oil (Fig. 22).

CHANGING THE OIL
Change the oil while the engine is still warm. The oil will flow freely 

and carry away more impurities.
1.  Remove the oil fill plug.
2.  Pour the oil out of the oil fill hole and into a container by 

tipping the unit to a vertical position (Fig. 23). Allow ample 

time for complete drainage.

3.  Wipe up any oil residue on the unit and clean up any oil that 

may have spilled. Dispose of the oil according to Federal, 

State and local regulations.

4.  Refill the crankcase with 2.03 fl.oz. (60 ml) of SAE 30 SJ oil 

(Fig. 25). 

NOTE:  Use the bottle and spout saved from initial use to 

measure the correct amount of oil. The fill line on the 

bottle’s label measures approximately 2.03 fl.oz. (60 ml) 

(Fig. 24).

5.  Check the level, See Checking the Oil Level.
6.  Once full, replace the oil plug.
AIR FILTER MAINTENANCE

Cleaning the Air Filter
Failure to maintain the air filter will VOID the warranty.
1.  To open the air filter cover, push the tab on the left side of the 

cover inward and pull the air filter cover slightly out and to the 

right (Fig. 26).

2.  Remove the air filter (Fig. 26).
3.  Wash the filter in detergent and water. Making sure to rinse the 

filter thoroughly and allow it to dry.

4.  Lightly coat the filter with clean SAE 30 motor oil.
5.  Squeeze the filter to spread and remove excess oil.
6.  Replace the filter.
NOTE:  Operating the unit without the air filter will VOID the 

warranty.

7.  To reinstall the air filter cover, position the hooks on the right 

side of the air filter cover into the slots at the right side of the 

back plate (Fig. 26). 

8.  Swing the cover to the left and press closed so the air filter cover tab snaps into the slot on the 

back plate (Fig. 26).

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. 27).
NOTE:  Careless adjustments can seriously damage to the unit. A qualified service dealer should 

make carburetor adjustments.

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 warm up according to the Starting/Stopping Instructions.
2.  Release the trigger and let the engine idle. If the engine stops, insert a small Phillips screwdriver in 

between the air filter cover and the engine cover (Fig. 27). Turn the idle speed screw 1/8 of a turn 

clockwise at a time until the engine idles smoothly.

3.  If the engine appears to be idling too fast, 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

take the unit to a qualified service dealer.
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.

• 

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 8 engine cover screws with the appropriate tool (Fig. 28), then remove the cover.
NOTE:  Make sure to store the screws so that they can be reinstalled into their original holes.
2.  Disconnect the spark plug wire.
3.  Clean dirt from around the spark plug and rocker arm cover. 

Remove the spark plug from the cylinder by turning a 5/8 in. 

socket counterclockwise.

4.  Remove the screw holding the rocker arm cover with the 

appropriate tool (Fig. 29). Remove the rocker arm cover and 

gasket.

5.  Turn the flywheel slowly to bring the piston to the top of its 

Fig. 23

Fig. 25

Fig. 31

MAINTENANCE INSTRUCTIONS

FREQUENCY

MAINTENANCE REQUIRED

SEE

Every 10 hours

Clean air filter

p. 5

After the first 10 

hours and every 

40 hours

Change oil
Check rocker arm to valve clearance and adjust
Check spark plug condition and gap

p. 5
p. 5
p. 5

WARNING:

 To avoid serious personal injury, 

always turn the unit off and allow it to cool before 

cleaning or maintaining it.

WARNING:

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

before cleaning or maintaining it.

Fig. 21

Oil Fill Line

Fig. 24

Fill Level

Fig. 27

Idle Adjustment 

Screw

Fig. 30

Rocker Arm

Adjustment Nut

0.003–0.006 in. 

(0.076–0.152 mm) 

Feeler Gauge

Valve 

Stem

Fig. 22

O-Ring

Oil Plug

Oil Fill Hole

Fig. 26

Air Filter Cover

Slot

Air Filter

Tab

Fig. 28

Screws

Screws

Fig. 29

Screw

Rocker 

Arm 

Cover

Spark 

Plug 

Hole

Fig. 32

0.025 in.

(0.635 mm)

WARNING:

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

could damage the cylinder.

CLEANING
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 are a.

• 

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 30 days. Dispose of the old gasoline in accordance with 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.

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 with 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.