MTD 4X90HU Owner’s Manual

Safe Operation Practices • Set-Up • Operation • Maintenance • Troubleshooting • Warranty

OperatOr’s Manual

547 cc OHV Vertical Shaft Engine

WARNING

READ AND FOLLOW ALL SAFETY RULES AND INSTRUCTIONS IN THIS MANUAL

BEFORE ATTEMPTING TO OPERATE THIS ENGINE.

FAILURE TO COMPLY WITH THESE INSTRUCTIONS MAY RESULT IN PERSONAL INJURY.

MTD LLC, P.O. BOX 361131 CLEVELAND, OHIO 44136-0019

Form No. 769-09649C

(July 21, 2017)

To The Owner

Thank You

This Operator’s Manual is an important part of your new engine. It will help you prepare and maintain the engine for the best
performance. Please read and understand the contents before operating the engine.

Table of Contents

1

Important Safe Operation Practices ..................... 3

Safety Labels............................................................ 5

Set-Up ....................................................................... 6

Controls & Features ................................................. 8

Operation ................................................................. 9

Maintenance & Adjustments .................................10

Troubleshooting .....................................................16

Replacement Parts .................................................17

Spanish ....................................................................21

Record Product Information

Before operating your new engine, please locate the model plate on the engine (shaded area in Figure below) and record the
information in the provided area below. This information will be necessary, should you seek technical support via our web site or with
your local dealer.

Model NuMber

Serial NuMber

Customer Support

Please do NOT return the machine to the retailer or dealer without first contacting the Customer Support Department.

If you have difficulty assembling this product, have questions regarding the controls, operation, or maintenance of this machine, want
to order replacement parts/attachments/accessories, or want to view an online How-To video; you can seek help from the experts. Have
your full model number and serial number ready. Choose from the options below:

◊ Visit us on the web: www.mtdproducts.com
◊ Call a Customer Support Representative at: [phone] or [phone]

◊ Write to: MTD LLC • P.O. Box 361131 • Cleveland, OH • 44136-0019

2

Important Safe Operation Practices

WARNING! This symbol points out important safety instructions which, if not followed,

could endanger the personal safety and/or property of yourself and others. Read and follow
all instructions in this manual before attempting to operate the equipment. Failure to
comply with these instructions may result in personal injury. When you see this symbol.

HEED ITS WARNING!

CALIFORNIA PROPOSITION 65

WARNING! Engine Exhaust, some of its constituents, and certain vehicle components

contain or emit chemicals known to State of California to cause cancer and birth defects
or other reproductive harm.

DANGER! This engine was built to be operated according to the safe operation practices in

this manual. As with any type of power equipment, carelessness or error on the part of the
operator can result in serious injury. Failure to observe the following safety instructions
could result in serious injury or death.

2

Training

1. Read, understand and follow all instructions on the engine
and in the manual(s) before attempting to assemble and
operate. Keep this manual in a safe place for future and
regular reference and for ordering replacement parts.

2. Be familiar with all controls and their proper operation.
Know how to stop the engine and disengage them quickly.

3. Never allow children under 14 years of age to operate the
engine. Children 14 and over should read and understand
the instructions and safe operation practices in this manual
and be trained and supervised by an adult.

4. Never allow adults to operate the machine without proper
instruction.

5. Keep the area of operation clear of all persons, particularly
small children and pets. Stop machine if anyone enters the
area.

Preparation

1. Wear sturdy, rough-soled work shoes and close fitting
slacks and shirts. Loose fitting clothes or jewelry can be
caught in the moving parts. Never operate the machine in
bare feet or sandals.

2. Disengage clutch levers and shift (if equipped) into neutral
(“N”) before starting the engine.

3. Never leave the engine running while unattended.

4. Never attempt to make any adjustments while the engine
is running, except where specifically recommended in the
operator’s manual.

Safe Handling of Gasoline:

To avoid personal injury or property damage, use extreme care
in handling gasoline. Gasoline is extremely flammable and the
vapors are explosive. Serious personal injury can occur when
gasoline is spilled on yourself and/or your clothes which can
ignite. Wash your skin and change clothes immediately.

1. When adding fuel, turn engine OFF and let engine cool at
least 2 minutes before removing the gas cap.

2. Fill fuel tank outdoors or in well ventilated area.

3. Use only an approved gasoline container.

4. Never fill containers inside a vehicle or on a truck or trailer
bed with a plastic liner. Always place containers on the
ground away from your vehicle before filling.

5. If possible, remove gas-powered equipment from the truck
or trailer and refuel it on the ground. If this is not possible,
then refuel such equipment on a trailer with a portable
container, rather than from a gasoline dispenser nozzle.

6. Keep the nozzle in contact with the rim of the fuel tank or
container opening at all times until fueling is complete. Do
not use a nozzle lock-open device.

3

7. Do not overfill fuel tank. Fill tank to full as indicated by
the fuel level indicator installed inside of the fuel tank or
marked on the tank. Do not over-fill to allow space for fuel
expansion. On some models, a fuel level indicator may NOT
be present, in this instance, fill the tank no more than 1/2
inch below the bottom of the filler neck to allow space for
fuel expansion.

8. Replace fuel cap and tighten until the cap ratchets.

9. If gasoline is spilled, wipe it off the engine and the
equipment. Move the machine to another area. Wait five
minutes before starting the engine.

10. To reduce fire hazards, keep the machine free of grass ,
leaves or other debris build up. Clean up oil or fuel spillage
and remove any fuel-soaked debris.

11. Keep gasoline away from sparks, open flames, pilot lights,
heat, and other ignition sources.

12. Never fuel equipment indoors because flammable vapors
will accumulate in the area.

13. Extinguish all cigarettes, cigars, pipes, and other sources of
ignition.

14. Check fuel line, tank, cap, and fittings frequently for cracks
or leaks. Replace if necessary.

Operation

1. When starting the engine, make sure spark plug, muffler,
and fuel cap are in place.

2. Do not crank engine with spark plug removed.

3. If fuel spills, wait until it evaporates before starting engine.

4. Allow muffler, engine cylinder, and fins to cool before
touching.

5. Keep children away from hot or running engines. They can
suffer burns from a hot muffler.

6. Remove accumulated combustibles from muffler and
cylinder area.

7. Operate equipment with all guards in place.

8. Keep hands and feet away from rotating parts.

9. Tie up long hair and remove jewelry.

10. Do not wear loose-fitting clothing, dangling drawstrings or
items that could become caught.

11. When starting the engine, pull cord slowly until resistance
is felt, then pull rapidly (if not electric start).

12. Remove all external equipment/engine loads before
starting engine.

13. Direct coupled equipment components such as, but not
limited to blades, impellers, pulleys, sprockets, etc., must
be securely attached.

Maintenance & Storage

1. Keep the engine in safe working order

2. Allow the engine to cool at least five minutes before
storing. Never tamper with safety devices. Check their
proper operation regularly.

3. Check bolts and screws for proper tightness at frequent
intervals to keep the engine in safe working condition.
Visually inspect the engine for any damage.

4. Before cleaning, repairing or inspecting; stop the
engine and make certain all moving parts have stopped.
Disconnect the spark plug wire and ground it against the
engine to prevent unintended starting.

5. Do not change the engine governor settings or over-speed
the engine. The governor controls the maximum safe
operating speed of the engine.

6. Maintain and replace safety and instruction labels as
necessar y.

7. Always refer to the operator’s manual for important details
if the machine is to be stored for an extended period of
time.

8. If the fuel tank has to be drained, do this outdoors.

9. Observe proper disposal laws and regulations for gas, oil,
etc. to protect the environment.

Do not modify engine

To avoid serious injury or death, do not modify engine in any
way. Tampering with the governor setting can lead to a runaway
engine and cause it to operate at unsafe speeds. Never tamper
with factory setting of engine governor.

Notice Regarding Emissions

Engines which are certified to comply with California and federal
EPA emission regulations for SORE (Small Off Road Equipment)
are certified to operate on regular unleaded gasoline, and
may include the following emission control systems: Engine
Modification (EM), Oxidizing Catalyst (OC), Secondary Air
Injection (SAI) and Three Way Catalyst (TWC) if so equipped.

Spark Arrestor

WARNING! This machine is equipped with an

internal combustion engine and should not be used
on or near any unimproved forest-covered, brush
covered or grass-covered land unless the engine’s
exhaust system is equipped with a spark arrestor
meeting applicable local or state laws (if any).

If a spark arrestor is used, it should be maintained in effective
working order by the operator. In the State of California the
above is required by law (Section 4442 of the California Public
Resources Code). Other states may have similar laws. Federal laws
apply on federal lands.
A spark arrestor for the muffler is available through your
nearest engine authorized service dealer or contact the service
department, P.O. Box 361131 Cleveland, Ohio 44136-0019.

4 Section 2 — important Safe operation practiceS

Safety Symbols

This page depicts and describes safety symbols that may appear on this product. Read, understand, and follow all instructions on the
machine before attempting to assemble and operate.

Symbol Description

READ THE OPERATOR’S MANUAL(S)
Read, understand, and follow all instructions in the manual(s) before attempting to
assemble and operate.

WARNING—GASOLINE IS FLAMMABLE
Allow the engine to cool at least two minutes before refueling.

WARNING— CARBON MONOXIDE
Never run an engine indoors or in a poorly ventilated area. Engine exhaust contains carbon
monoxide, an odorless and deadly gas.

WARNING— ELECTRICAL SHOCK
Do not use the engine’s electric starter in the rain.

WARNING— HOT SURFACE
Engine parts, especially the muffler, become extremely hot during operation. Allow engine
and muffler to cool before touching.

WARNING! Your Responsibility — Restrict the use of this power machine to persons who read, understand and

follow the warnings and instructions in this manual and on the machine.

SAVE THESE INSTRUCTIONS!

5Section 2 — important Safe operation practiceS

Set-Up

-30º -20º -10º 0º

0º 15º 30º 50º 70º 85º 105º

10º 20º 30º 40º

-20º

(ºC)
(ºF)

5W-30

30

10W-30

Sintético 5W-30

3

Gas & Oil

NOTE: The engine is shipped without gasoline and with motor
oil in the engine. However, you MUST check the oil level before
operating. Be careful not to overfill. Running the engine with
insufficient oil can cause serious engine damage and void the
engine warranty.

WARNING! Always keep hands and feet clear of

equipment moving parts. Do not use a pressurized
starting fluid. Vapors are flammable.

Oil Recommendations

Before starting engine, check oil level, capacity is 1800 ml/57.5 fl.
oz. Refer to viscosity chart in Figure 3-1 for oil recommendations.
Do not over-fill. Use a 4-stroke, or an equivalent high detergent,
premium quality motor oil certified to meet or exceed
U.S. automobile manufacturer’s requirements for service
classification of a minimum level SJ (higher letter ratings are
acceptable such as SL and SM grades). Motor oil will display this
designation on the container.

SAE 10W-30 is recommended for general, all temperature use. If
single viscosity oil is used, select the appropriate viscosity for the
average temperature in your area from the chart below.

Checking Oil Level

NOTE: Be sure to check the oil while on a level surface with the
engine stopped.

1. Remove the oil filler cap/dipstick and wipe the dipstick
clean.

2. Insert the dipstick into the oil filler neck. Turn the dipstick
a 1/4 turn into the locked position to fully seat. See Figure
3-2.

Upper

Nivel

Level

Superior

Figure 3-1

CAUTION: Do not use non-detergent oil or 2-stroke engine oil. It
could shorten the engine’s service life.

NOTE: A 5w30 synthetic oil may be used to improve start ability
for cold weather (temperatures below 40 F).

Figure 3-2

3. Remove dipstick to check the oil level.

4. If the level is low, slowly add oil to the upper limit on the
dipstick. See Figure 3-2 inset.

5. Reinsert the dipstick and turn to the locked position before
starting the engine.

NOTE: Do not overfill. Overfilling with oil may cause
smoking, hard starting, spark plug fouling, hydraulic lock,
or oil saturation of air cleaner.

6

Fuel Requirements

CAUTION: Operating the engine with E15 or E85

fuel, an oil/gasoline mixture, dirty gasoline, or
gasoline over 30 days old without fuel stabilizing
additive may result in damage to your engine’s
carburetor. Subsequent damage would not be
covered under the manufacturer’s warranty.

Use automotive gasoline (unleaded or low leaded to minimize
combustion chamber deposits) with a minimum of 87 octane.
Gasoline with up to 10% ethanol (E10) or 15% MTBE (Methyl
Tertiary Butyl Ether) can be used. Never use an oil/gasoline
mixture or dirty gasoline. Avoid getting dirt, dust, or water in the
fuel tank. DO NOT use E15 or E85 gasoline.

WARNING! Gasoline is extremely flammable and is

explosive under certain conditions.

• Refuel in a well-ventilated area with the engine stopped. Do
not smoke or allow flames or sparks in the area where the
engine is refueled or where gasoline is stored.

• Do not overfill the fuel tank. After refueling, make sure the
tank cap is closed properly and securely.

• Be careful not to spill fuel when refueling. Spilled fuel or
fuel vapor may ignite. If any fuel is spilled, make sure the
area is dry before starting the engine.

• Avoid repeated or prolonged contact with skin or breathing
of vapor.

Adding Fuel

WARNING! An adult should fuel this engine. NEVER

allow children to refuel the engine. Gasoline (fuel)
vapors are highly flammable and can explode. Fuel
vapors can spread and be ignited by a spark or flame
many feet away from engine. To prevent injury or
death from fuel fires, follow these instructions:

• DO NOT use leaded fuel.

• Fuel must be fresh and clean. NEVER use fuel left over
from last season or stored for long periods.

• NEVER mix oil with fuel in this engine.

• DO NOT use fuel containing Methanol (Wood
Alcohol)

NOTE: Before refueling, allow engine to cool two minutes.

1. Clean around fuel fill before removing cap to fuel.

2. Fill tank until fuel reaches ⁄ inch below the bottom of the
filler neck to allow space for fuel expansion. Be careful not
to overfill.

3. Replace the fuel cap and tighten securely. Wipe up spilled
fuel before starting engine. If fuel is spilled DO NOT start
engine. Move machine away from area of spillage. Avoid
creating any source of ignition until fuel vapors are gone.

7Section 3 — Set-Up

Controls and Features

Finger Guard

Oil Drain

Carburetor

Fuel Filter

Electric

Starter

Oil Filter

Spark Plug

Air Cleaner

Oil Fill Cap

4

Throttle/Choke Control

The throttle/choke control is located on the mower and is used to
aid in starting/stopping the engine and adjusting engine speeds.
Refer to the Controls and Features section of the mower manual
for more information regarding this control.

Oil Drain

Removing the oil drain plug will drain the oil from the engine.
The engine is equipped with a side drain.

Figure 4-1

Oil Fill Cap

Remove the oil fill cap to check the oil level and add oil.

Fuel Cap

Remove the fuel cap to add fuel. Refer to the Controls and
Features section of the lawn mower’s manual for the location of
the fuel cap.

8

Operation

Stop

Position

Start

Position

Run

Position

Pre-Operation Check

The engine is shipped without gasoline and with oil in the
engine. See the Set-Up Section of this manual for instructions on
adding gasoline and checking oil.

Starting the Engine

1. Release all controls on the mower.

2. Move the gear shift lever into the neutral (N) position.

3. If starting a cold engine, place the
throttle/choke control all the way
forward, into the CHOKE position.

Note: Use of choke may not be
necessary if the engine is warm or
the air temperature is high.

4. Insert the key into the ignition
switch.

5. Turn the ignition key clockwise
to the START position. After the
engine starts, release the key. It
will return to the RUN position.
See Figure 5-1.

CAUTION: Do NOT hold the key in the START

position for longer than five seconds at a time.
Doing so may cause damage to your engine’s
electric starter.

6. Move the throttle/choke control into the FAST (rabbit)
position.

NOTE: Never leave the throttle/choke control in the CHOKE
while operating the mower. Doing so will result in a “rich”
fuel mixture and cause the engine to run poorly.

Choke

Fast

Slow

5

Figure 5-1

Stopping the Engine

WARNING! If you strike a foreign object, stop the

engine and remove the ignition key (if so equipped).
Thoroughly inspect the machine for any damage.
Repair the damage before restarting and operating.

1. If the blades are engaged, disengage the PTO.

2. Turn the ignition key counterclockwise to the STOP
position.

3. Remove the key from the ignition switch to prevent
unintended starting.

9

Engine Maintenance

6

WARNING: Shut off the engine before performing

any maintenance. To prevent accidental start-up,
disconnect the spark plug boot.

Maintenance Schedule

Check Engine Oil Level

Change Engine Oil ††

Change Engine Oil FIlter ††

Check Air Cleaner

Periodic inspection and adjustment of the engine is essential if
high level performance is to be maintained. Regular maintenance
will also ensure a long service life. The required service intervals
and the kind of maintenance to be performed are described
in the table below. Follow the hourly or calendar intervals,
whichever occur first. More frequent service is required when
operating in adverse conditions.

WARNING: If the engine has been running, the

muffler will be very hot. Be careful not to touch the
muffler.

After First 5

Hours

Each use or

Every 5-10

Hrs.

Every Season

or 25 Hours

P

P P

P

Every season
or 100 Hours

P

Service Dates

Service Air Cleaner †

Check Spark Plug

Replace Spark Plug

Clean Cooling Fins

Clean Finger Guard and around Muffler

† Service more frequently when used in dusty areas.
†† Every season or 25 hours if operating under heavy load or high ambient temperature.

P

P

P

P

P

10

Oil Service

Oil Fill Cap

Drain

Plug

Oil Filter

• Check oil level regularly.

• Be sure correct oil level is maintained. Check every five
to ten hours before starting engine. See oil checking
procedure in the Set-Up section.

Oil Drain

IMPORTANT: Be sure to check engine on a level surface with the
engine stopped. Drain the oil while the engine is still warm to
assure rapid and complete draining.

1. Remove all fuel from tank by running engine until it stops
from lack of fuel.

2. Remove drain plug and allow oil to drain into a suitable
container. See Figure 6-1.

Figure 6-1

3. Reinstall the drain plug and tighten it securely, 12-14 Nm
(106.2-123.9 in-lb).

IMPORTANT: Used motor oil may cause skin cancer if repeatedly
left in contact with the skin for prolonged periods. Although this
is unlikely unless you handle used oil on a daily basis, it is still
advisable to thoroughly wash your hands with soap and water as
soon as possible after handling used oil.

NOTE: Please dispose of used motor oil in a manner that is
compatible with the environment. Check with your local
municipality for proper disposal procedure. Do not throw it in
the trash or pour it on the ground.

Replace Oil Filter

This engine is equipped with a spin-on oil filter that should be
replaced each time an oil change is performed, every season or
100 hours. Refer to Figure 6-2.

Figure 6-2

1. Drain oil. See oil drain section.

2. Remove oil filter. Dispose of old oil filter properly.

3. Lube gasket of new oil filter with clean oil.

4. Install and turn oil filter by hand until the gasket comes in
contact with the sealing surface of the crankcase cover,
then tighten the oil filter, 10-12 Nm (88.5-106.2 in-lb), 1/2­3/4 turn.

5. Add oil. See add oil section.

6. Make sure dipstick is installed.

7. Start and run engine. Check for leaks.

8. Stop engine. Wait a few minutes and check the oil level.
See checking oil level section.

9. Install and tighten dipstick.

11Section 6 — Maintenance

2

1

Air Filter

Cover

Thumb

Screw

1

2

Add Oil

IMPORTANT: Be sure to check engine on a level surface with the
engine stopped.

1. Wipe around dipstick cap and tube with a clean cloth to
remove any debris. See Figure 6-3.

Figure 6-3

2. Remove dipstick and wipe clean with a cloth.

3. Pour oil into the dipstick tube. Do not over fill. With an oil
filter change the high level amount of oil for this engine is
1700 ml (57.48 fl-oz.).

4. Install dipstick and turn to locked position before starting
engine.

5. Start engine. Allow to run for a few seconds and then shut
down the engine.

6. Check the oil level. See Checking Oil Level section.

1. Unscrew a 1/4 turn and remove the thumb screws.

2. Remove the air filter cover. See Figure 6-4.

Figure 6-4

3. Pull up on an angle and then forward to remove the air
filter. See Figure 6-5.

Air Filter Service

Paper filters cannot be cleaned and should be replaced every
100 operating hours; more often if used in extremely dusty
conditions.

WARNING: Never use gasoline or low flash point

solvents for cleaning the air filter element. A fire or
explosion could result.

IMPORTANT: Never run the engine without the air filter. Rapid
engine wear will result.

12 Section 6 — Maintenance

Figure 6-5