Honda UMC425, UMC435 Owner's Manual

INTRODUCTION

©

INTRODUCTION....................................1

SAFETY MESSAGES..............................1

SAFETY INFORMATION......................2

SAFETY LABEL LOCATION ................4

INITIAL POWERHEAD SETUP

...............4

COMPONENT & CONTROL

LOCATIONS............................................5

POWERHEAD ATTACHMENTS.........5

CONTROLS .............................................6

BEFORE OPERATION CHECKS.......... 7

OPERATION......................................... 10

SAFE OPERATING

PRECAUTIONS............................... 10

STARTING THE ENGINE .............. 11

SETTING ENGINE SPEED

............... 12

STOPPING THE ENGINE.............. 12

SERVICING YOUR

POWERHEAD...................................... 12

THE IMPORTANCE OF

MAINTENANCE ............................. 12

MAINTENANCE SAFETY

.............. 12

SAFETY PRECAUTIONS............... 13

MAINTENANCE

SCHEDULE ......................................13

REFUELING ..................................... 14

ENGINE OIL..................................... 14

Recommended Oil.................. 14

Oil Level Check......................... 14

Oil Change ................................. 15

AIR CLEANER.................................. 16

Inspection .................................. 16

Cleaning ..................................... 16

THROTTLE CABLE..........................16

Check and Adjustment

...........16

Free Play Inspection................16

SPARK PLUG ...................................17

COOLING FINS ...............................18

FUEL FILTER AND FUEL

TANK .................................................18

FUEL TUBE....................................... 18

SPARK ARRESTER (applicable

types) ................................................ 19

HELPFUL TIPS &

SUGGESTIONS ....................................20

STORING YOUR

POWERHEAD.................................. 20

TRANSPORTING.............................21

TAKING CARE OF UNEXPECTED
PROBLEMS

...........................................22

TECHNICAL & CONSUMER

INFORMATION....................................22

Serial Number Location .............22

Carburetor Modifications for

High Altitude Operation ............23

Emission Control System

Information.....................................23

Emission Control System

Warranty..........................................24

Specifications.................................25

Tuneup Specifications................25

Quick Reference

Information.....................................25

CONSUMER INFORMATION

...............26

Customer Service
Information (For USA and

Canada)............................................26

Thank you for purchasing a Honda powerhead. We want to help you to
get the best results from your new powerhead and to operate it safely.
This manual contains information on how to do that; please read it
carefully before operating the powerhead. If a problem should arise, or if
you have any questions about your powerhead, consult an authorized
Honda servicing dealer.

All information in this publication is based on the latest product
information available at the time of printing. Honda Motor Co., Ltd.
reserves the right to make changes at any time without notice and
without incurring any obligation. No part of this publication may be
reproduced without written permission.

This manual should be considered a permanent part of the powerhead
and should remain with the powerhead if resold.

We suggest you read the Distributor's Limited Warranty (U.S.) /Distributor's
Warranty (CA.) to fully understand its coverage and your responsibilities
of ownership. The Distributor's Limited Warranty (U.S.) / Distributor's
Warranty (CA.) is a separate document that should have been given to
you by your dealer.
If not, you can obtain a copy from your dealer or download from:
U.S.A http://powerequipment.honda.com/support/warranty
Canada http://powerequipment.honda.ca/parts-service/warranty

SAFETY MESSAGES

OWNER’S MANUAL

UMC425·UMC435

POWERHEAD

The engine exhaust from this product contains

chemicals known to the State of California to

cause cancer, birth defects or other reproductive

harm.

Your safety and the safety of others are very important. We have
provided important safety messages in this manual and on the
powerhead. Please read these messages carefully.

A safety message alerts you to potential hazards that could hurt you or

others. Each safety message is preceded by a safety alert symbol and one
of three words, DANGER, WARNING, or CAUTION.

These signal words mean:

You WILL be KILLED or SERIOUSLY HURT if
you don’t follow instructions.

You CAN be KILLED or SERIOUSLY HURT if

Each message tells you what the hazard is, what can happen, and what
you can do to avoid or reduce injury.

DAMAGE PREVENTION MESSAGES

You will also see other important messages that are preceded by the
word NOTICE.

This word means:

The purpose of these messages is to help prevent damage to your
powerhead, other property, or the environment.

The illustrations in this manual are based on: UMC435

• The illustrations may vary according to the type.

2022 Honda Motor Co., Ltd. –All Rights Reserved

31VP8607
00X31-VP8-6070

Your powerhead, other property, or the environment can be
damaged if you don't follow instructions.

you don’t follow instructions.

You CAN be HURT if you don’t follow
instructions.

UMC425A/C·UMC435A/C

CONTENTS

1

SAFETY INFORMATION

HARD HAT

EAR HEARING
PROTECTION

CLOTHES
(LONG SLEEVE)

CLOTHES (LONG PANTS)

LEG PROTECTORS

SAFETY BOOTS (WITH TOE
PROTECTOR)

GLOVES

FACE S HIELD

EYE PROTECTION

ARM COVERS

Operator Responsibility

• Understand the operation of all controls and learn how to stop the
engine quickly in case of an emergency. Make sure the operator
receives adequate instruction before operating the equipment.

• Do not allow children to operate the powerhead. Keep children and
pets away from the area of operation.

• Your powerhead’s exhaust contains poisonous carbon monoxide. Do
not run the engine without adequate ventilation, and never run the
engine indoors.

• The powerhead and exhaust become very hot during operation.

• Only use Honda approved attachments. If not, injury or accident may
occur.

• Read and follow the instructions in the owner’s manual that came with
each attachment.

• Never operate the powerhead when tired, ill, or under the influence of
alcohol or other drugs.

• Any part of the machine is a potential source of danger if the machine
is used in abnormal conditions or if the maintenance is not performed
correctly.

• If you lend or resell your powerhead to a third person, instruct him or
her on how to handle the product and alert him or her to read the
Owner’s Manual carefully before operation.

• Follow the instructions in the owner’s manual that comes with each
attachment.

• Keep in mind that the operator or user is responsible for any accidents
or hazards that may occur to other people or their property.

• While operating the powerhead, always wear protective clothing and
protective devices.

• Follow the instructions in the owner’s manual that comes with each
attachment, regarding required protective clothing and protective
devices. For example:
– Protective clothing

Wear adequate clothes with long sleeves and long pants.
Do not wear loose or baggy clothing.
Arm covers and leg protectors should be worn.
Do not wear anything around your neck (for example necklaces or
neckties).
Tie your hair if it is long.

– Protective devices

* Eye protection

Eye protection should meet the requirements of ANSI Z87.1.
Wear safety glasses or other eye protection to protect your eyes
from flying debris.

*Hard hat

Wear a hard hat to protect your head from any overhead branches
and falling foreign material.

* Face shield

Wear a face shield to protect your face from flying debris.

* Ear hearing protection

To reduce the risk of hearing loss, hearing protection is required.

*Gloves

Wear gloves to protect your hands.

* Safety boots

Wear safety boots with a non-slip sole and toe protector to protect
your feet from falling objects and flying debris.
Do not operate the equipment barefoot or wearing open sandals.

* Leg protectors

We recommend that you wear the leg protectors to protect your
legs.

* Dust mask

We recommend that you wear a dust mask to protect yourself
from dust and pollen.

• Before each use, visually inspect the powerhead for any damage and
looseness of parts.

• Before each use, look around and underneath the engine for signs of
oil or gasoline leaks.

• Avoid operating the powerhead at night, in poor visibility or in bad
weather.

• Walk, never run during operation.

• Avoid operating the powerhead on a steep slope.
The steep slope may be slippery, causing you to fall.

• Do not operate the powerhead with any labels, or any parts removed.

• Do not tamper with the powerhead as it can result in personal injury
and/or equipment damage.

• Only use attachments that are designed for your model and
application.

• Stop the engine by moving the engine switch to the OFF position in
the following cases:
– Before any operation around the powerhead.
– Before checking, cleaning or working on the powerhead.
– After dropping or striking a foreign object. Inspect the powerhead

for damage and make repairs before restarting the powerhead.

– If the powerhead starts to vibrate abnormally. Check immediately

the cause of the vibration and perform the necessary repair.
– Whenever you leave the powerhead unattended.
– Before refueling.
– When any person or pet is approaching.
– Shut off the engine immediately when the powerhead shows

abnormal vibration suddenly. Sudden vibration can suggest the

damaged rotating parts or loose fasteners. Examine the cause of the

problem, and do not start the engine before a repair is made.

• The attachment should not be moving when the engine is at idle. If this
happens, contact your authorized Honda dealer. This idle speed will
need to be adjusted. Make sure the cutting attachment has stopped
before the unit is set down.

• Keep all nuts, bolts and screws tight to be sure the powerhead is in a
safe working condition. Regular maintenance is essential to user’s
safety and product performance.

• Do not use the powerhead with worn or damaged parts. Parts must be
replaced, or repaired. Replace worn or damaged part

s with Honda
genuine parts. Non equivalent quality parts may damage the machine
and be prejudicial to your safety.

2

• Injury caused by vibration and cold:
You may feel the prickling or burning pain in your fingers, and the
fingers may lose color and feeling. It is believed that these symptoms
are brought by vibration and/or exposure to cold. The specific trigger
point of these symptoms are not identified yet, but observe the
following instructions.

* Limit the amount of time you spend operating the powerhead in a

day.
* Keep your body warm, especially your hands, wrists and arms.
* Take your breaks at short intervals. Do not smoke while working.
* When you feel discomfort, redness and swelling of the fingers

followed by whitening and loss of feeling, consult your doctor

promptly.

• Injury caused by repeated operation:
Performing the repeated operation for a prolonged time may cause
injury. Observe the following instructions to reduce the causes of the
injury.

* Avoid repeated operation by using your wrist(s) in bent, stretched

or twisted position.

* Take your breaks regularly to minimize the effect of repeated

operation. Take your time when performing repeated operation.
Do not rush to operate the powerhead.

* When your fingers, hands, wrists and/or arms are throbbing or

numbed, consult your doctor.

Child Safety

Carbon Monoxide Hazard

Your powerhead’s exhaust contains poisonous carbon monoxide gas,
which you cannot see or smell. Breathing carbon monoxide can KILL YOU
IN MINUTES.
For your safety:

• Do not start or operate the engine in any closed or partially enclosed
area, such as a garage.

• Never run the powerhead in a closed or even partially closed area
where people or pets may be present.

• Never operate the powerhead near open doors, windows, or vents.

• Get fresh air and seek medical attention immediately if you suspect
you have inhaled carbon monoxide.

Early symptoms of carbon monoxide exposure include headache, fatigue,
shortness of breath, nausea, and dizziness. Continued exposure to
carbon monoxide can cause loss of muscular coordination, loss of
consciousness, and then death.

• Keep children indoors and supervised at all times when any outdoor
powerhead is being used nearby.

• Never assume children will remain where you last saw them. Be alert
and turn the powerhead off if children enter the area.

• Children should never be allowed to operate the powerhead, even
under adult supervision.

Fire and Burn Hazard

Gasoline is extremely flammable, and gasoline vapor can explode.
Use extreme care when handling gasoline. Keep gasoline out of reach of
children.

• Store fuel in containers specifically designed for this purpose.

• Refuel outdoors only, and do not smoke while refueling or handling
fuel.

• Add fuel before starting the engine. Never remove the cap of the fuel
tank or add gasoline while the engine is running or when the engine is
hot.

• If gasoline is spilled, do not attempt to start the engine but move the
powerhead away from the area of spillage and avoid creating any
source of ignition until gasoline vapors have dissipated.

• Tighten the fuel tank and container cap securely.

• When you start the engine after refueling, be sure to start the engine at
least 10 feet (3 meter) away from the refueling spot.

• Never store the powerhead with gasoline in the tank inside a building
where fumes may reach an open flame, spark or high temperature
source.

• Allow the engine to cool before storing in any enclosure.

• To reduce a fire hazard, keep the powerhead, especially the engine,
muffler, and gasoline storage area, free of grass, leaves, or excessive
grease.

• If the fuel tank has to be drained, this should be done outdoors, with a
cold engine.

• Do not overfill the fuel tank.

• Make sure that any spilled fuel has been wiped up and cleaned before
starting the engine.

• Never smoke near gasoline.

3

SAFETY LABEL LOCATION

Operation of This Equipment May Create
Sparks That Can Start Fires Around Dry
Vegetation. A Spark Arrestor May be
Required. The Operator Should Contact
Local Fire Agencies For Laws or
Regulations Relating to Fire Prevention
Requirements.

Per California Public Resources Code 4442.6

USA model

Canadian model only

French labels come with the powerhead.

(1)

(4)

(2) (3)

(5)

INITIAL POWERHEAD SETUP

These labels warn you of potential hazards that can cause serious injury.
Read them carefully.
If a label comes off or becomes hard to read, contact your servicing
dealer for replacement.

Importance of Proper Assembly

Proper assembly is essential to operator safety and the reliability of the
machine. Any error or oversight made by the person assembling and
servicing a machine can result in faulty operation, damage to the
machine, or injury to the operator.

Improper assembly can cause an unsafe condition that can
lead to serious injury or death.

Follow the procedures and precautions in the assembly
instructions carefully.

List of Loose Parts

Carefully remove the powerhead and loose parts from the carton and
compare the loose parts against the following list. Contact the authorized
Honda dealer from whom you purchased the powerhead if any of the
loose parts shown are not included with your powerhead.

4

Ref.

OIL FILLER CAP/DIPSTICK

OIL FILLER
OPENING

THROTTLE TRIGGER
INTERLOCK

ENGINE SWITCH

LOOP HANDLE

MAIN PIPE

SET PIN KNOB

JOINT KNOB

PROTECTOR

HANGER

THROTTLE TRIGGER

SPARK PLUG

SPARK PLUG CAP
(inside the top cover)

TOP COVER

AIR CLEANER

PRIMING
PUMP

CHOKE LEVER

FUEL RETURN TUBE

FUEL TUBE

FUEL TANK CAP

STARTER GRIP

ENGINE OIL FILLER CAP

MUFFLER

Description UMC425 UMC435 Qty.

No.

Owner’s

(1)

Manual

••1

Single-strap

(2)

carrying

•1

harness

Double-strap

(3)

carrying

•1

harness

(4) hex wrench • • 1

Spark plug

(5)

wrench

••1

Add Engine Oil

The powerhead is shipped WITHOUT OIL in the engine.
Place the powerhead on a level
surface, and then remove the
oil filler cap/dipstick.
All Honda engines are run at
the factory prior to packaging.
Most of the oil is removed prior
to shipment; however, some oil
remains in the engine. The
amount of oil left in the engine
varies.
Add enough recommended oil
(page 14) to bring the oil level to the lower edge of the oil filler opening.
Do not overfill the engine with oil, as the oil tank capacity is small.

Running the engine with too little or too much oil can cause engine damage.
This type of damage is not covered under the Distributor’s Limited Warranty
(U.S.) / Distributor’s Warranty (CA.). Screw in the oil filler cap/dipstick
securely.

COMPONENT & CONTROL LOCATIONS

Please Register Your Powerhead

Please take a few minutes and register your purchase with Honda.
You can register by completing and mailing the registration card
provided with the powerhead or going online to
powerequipment.honda.com and clicking on Product Registration.

Before Using Your Powerhead

Before using the powerhead, all operators must read the following
sections:

• SAFETY INFORMATION (page 2)

• CONTROLS (page 6)

• BEFORE OPERATION CHECKS (page 7)

• OPERATION (page 10)

• MAINTENANCE SCHEDULE (page 13)

POWERHEAD ATTACHMENTS

The following Honda approved attachments can be used with the
powerhead. Consult your servicing dealer.

• Trimmer/Brush Cutter

•Edger
∙∙∙etc.

5

CONTROLS

OFF ON

ENGINE SWITCH

OFF

ON

PRIMING PUMP

CHOKE LEVER

CLOSED

OPEN

CLOSED

OPEN

STARTER GRIP

THROTTLE TRIGGER
INTERLOCK

FAS T

SLOW

THROTTLE TRIGGER

Starter Grip

Engine Switch

The engine switch enables and disables the ignition system.
The engine switch must be in the ON position for the engine to run.
Moving the engine switch to the OFF position stops the engine.

Priming Pump

Pressing the priming pump feeds the gasoline from the fuel tank to the
carburetor. This procedure is necessary for starting the engine (see page

11).

Pulling the starter grip operates the recoil starter to crank the engine for
starting.

Throttle Trigger

The throttle trigger controls engine speed.
Pulling and releasing the throttle trigger shown below makes the engine
run faster or slower.

The throttle trigger interlock must be depressed before the throttle
trigger can be activated.

Choke Lever

The choke lever opens and closes the choke valve in the carburetor.
The CLOSED position enriches the fuel mixture for starting a cold engine.
The OPEN position provides the correct fuel mixture for operation after
starting, and for restarting a warm engine.

By pulling the throttle trigger gradually, the engine speed increases
gradually.
Pull the throttle trigger more to accelerate the engine speed.
By releasing the throttle trigger, the engine speed decreases.

Throttle Trigger Interlock

The throttle trigger interlock makes the throttle trigger operable. The
throttle trigger cannot be pulled unless the throttle trigger interlock has
been pushed beforehand.

6

Joint

JOINT

QUICK-RELEASE
LATCH TAB

CARRYING
HARNESS

QUICK-RELEASE LATCH

BEFORE OPERATION CHECKS

The joint is to attach a Honda approved attachment to the powerhead.
Refer to Pages 8–9 for how to attach and detach the attachments.

Carrying Harness Quick-Release Latch

The quick-release latch tab is provided to detach the powerhead from
your body in an emergency.
Pull up the quick-release latch tab, and the powerhead is detached from
the carrying harness.

IS YOUR POWERHEAD READY TO GO?

For your safety, to ensure compliance with environmental regulations,
and to maximize the service life of your equipment, it is very important to
take a few moments before you operate the powerhead to check its
condition. Be sure to take care of any problem you find, or have your
servicing dealer correct it, before you operate the powerhead.

Failure to properly maintain this powerhead, or failing to
correct a problem before operation, could result in a
significant malfunction.

Some malfunctions can cause serious injuries or death.

Always perform a pre-operation inspection before each
operation and correct any problems.

Before beginning your pre-operation checks, be sure the powerhead is
level and the engine switch is in the OFF position.

Always check the following items before you start the engine:

Check the General Condition of the Powerhead

1. Before each use, look around and underneath the engine for signs of
oil or gasoline leaks.

2. Remove any excessive dirt or debris, especially around the muffler
and recoil starter.

3. Look for signs of damage.

4. Check that all shields and covers are in place, and all nuts, bolts, and
screws are tightened.

Adjustment of the Carrying Harness

Failure to wear the carrying harness while using the
powerhead could result in instability.

Injuries may occur due to instability.

Be sure to wear the carrying harness before using the
powerhead.

1. Wear the carrying harness so that the hip pad is on the right side of
your body.

• Make sure the harness does not twist.

• If the carrying harness is for both shoulders, firmly secure the

carrying harness latch on the front of your body until it clicks.
To unlock the carrying harness latch, pull the harness to the right
and to the left while pressing the latch.

7

2. Adjust the length of the harness as shown in the figures below.

For both shoulders

(UMC435)

For single shoulders

(UMC425)

CARRYING
HARNESS

CARRYING
HARNESS

HIP PAD

CARRYING
HARNESS
LATCH

HIP PAD

To make it shorter To make it longer

1

2

2

1

(UMC435) (UMC425)

Roll the end of the harness
and fasten it.
(There is one applicable
point on the back side of
your body)

Roll the end of the
harness and fasten it.

QUICK-RELEASE
LATCH TAB

HOOK

QUICK-RELEASE
LATCH

HIP PAD

LATCH TONGU E

SLOT

JOINT HOLDER SET PIN KNOB (Back side of the portion where

the attachment is connected)

KEY

PROJECTION

JOINT KNOB

AT TAC H M EN T

JOINT HOLDER

GROOVE

LOOS EN

LOCK

1

2

3

3. Insert the latch tongue in the slot of the quick-release latch to
reattach the powerhead to the carrying harness.

If the latch is not released, have your device inspected and repaired by
your servicing dealer.

Attachment Installation/Removal

Check the joint area:

1. Check to see if the set pin knob moves smoothly.

3. Roll the end of the harness toward your body and fasten it.

Check the Quick-Release Latch

1. Put on the carrying harness.

2. Check that the latch is released as soon as the quick-release latch tab
is pulled upwards while holding the hip pad with your left hand.

8

2. Check to see if the joint knob tightens and loosens smoothly, and if
there is any damage.

3. Make sure there is no debris in the groove and inside the joint holder.

Installation:

Running this engine without an attachment in place could
cause an unsafe condition.

Moving parts could cause severe injury.

Do not run the engine without an attachment properly
secured.

1. Turn the set pin knob to the lock position and loosen the joint knob.

2. Align the “ ” mark on the attachment with the joint projection
which also aligns the key of the attachment with the joint groove.

3. Insert the attachment until the set pin knob clicks. Confirm the “ ”

JOINT HOLDER

AT TAC HM EN T

SET PIN KNOB

JOINT HOLDER

AT TAC H M EN T

JOINT KNOB

TIGHTEN

4

5

SET PIN KNOB

UNLOCK

JOINT KNOB

LOOS EN

1

2

MAIN PIPE

AT TAC H M EN T

POWERHEAD SIDE

SET PIN KNOB

LOCK

mark on the attachment is at the joint holder end.

4. Pull the attachment and joint holder to the arrow direction to check
that the attachment will not come loose.

5. Tighten the joint knob.

3. Hold the main pipe on the powerhead side and detach the
attachment.

4. Turn the set pin knob to the lock position.

Check the Engine

When you place the powerhead with the recoil starter facing down, be
careful not to damage the recoil starter. Recoil starter or the engine
might get damaged from the impact.

Removal:

Be sure to turn the engine switch to the OFF position. The
attachment will continue to move briefly after the engine
has stopped or the throttle trigger is released.

A moving attachment can cause injury.

Maintain proper control of the powerhead until the
attachment has completely stopped moving.

1. Loosen the joint knob.

2. Pull the set pin knob up and twist 90 degrees to the unlock position.

1. Check the fuel level (see page 14). Starting with a full tank will help to
eliminate or reduce operating interruptions for refueling.

2. Check the engine oil level (see page 14). Running the engine with a
low oil level can cause engine damage.

3. Check the air filter element (see page 16). A dirty air filter element will
restrict air flow to the carburetor, reducing engine and powerhead
performance. A damaged air filter element will allow dust to enter
and damage the engine.

4. Check the throttle cable free play (see page 16). Operate the throttle
system several times and check if it the free play (i.e. throttle lever
does not move while operating the throttle trigger).

9

Check All Bolts and Nuts

THROTTLE ASSEMBLY

HANDLE MOUNTING BOLTS (4)

LOOP HANDLE

HOOK

QUICK-RELEASE
LATCH TAB

OPERATION

1. Check each bolt and nut for looseness. Tighten them securely if
necessary.

2. Check the handle for loose mounting bolts, and tighten them
securely if necessary.

SAFE OPERATING PRECAUTIONS

Before operating the powerhead for the first time, please review the

SAFETY INFORMATION (see pages 2–3) and the BEFORE OPERATION
CHECKS (see pages 7–10).

For your safety, do not operate the powerhead in an enclosed area such
as a garage. Your powerhead’s exhaust contains poisonous carbon
monoxide gas that can collect rapidly in an enclosed area and cause
illness or death.

Exhaust contains poisonous carbon monoxide gas that can
build up to dangerous levels in closed areas.

Breathing carbon monoxide can cause unconsciousness or
death.

Never run this product's engine in a closed, or even partly
closed area.

Read and understand the safety instructions on pages 7 to 10 before
operating the powerhead.

If you notice any abnormal sound, smell, vibration, or other unusual
signs, stop the engine immediately and consult your authorized Honda
dealer.

With the engine idling, hook the powerhead to your carrying harness and
hold the powerhead at the correct position.

Hold the powerhead firmly with both hands, with your fingers and
thumbs encircling the handles as shown. This will help you to keep the
powerhead under control at all times.

For how to use the attachment, read and follow the instructions in the
owner’s manual that came with each attachment.

In an emergency, pull up on the quick-release latch tab to detach the
powerhead from the carrying harness.

10

STARTING THE ENGINE

ENGINE SWITCH

ON

ON

CHOKE LEVER

CLOSED

OPEN

CLOSED

OPEN

PRIMING PUMP FUEL RETURN TUBE

STARTER GRIP

MAIN PIPE

Direction
to pull

CHOKE LEVER

OPEN

OPEN

Exhaust contains poisonous carbon monoxide gas that can
build up to dangerous levels in closed areas.

Breathing carbon monoxide can cause unconsciousness or
death.

Never run this product's engine in a closed, or even partly
closed area.

Start the engine in a place away from the people, pets, and surrounding
buildings. Be sure there are no obstacles in the working area.

1. Move the engine switch to the ON position.

3. To start a cold engine, press the priming pump several times until the
priming pump is filled with fuel.
Even if the priming pump is pressed too many times, the extra fuel
will return to the fuel tank.
If the priming pump is not pressed enough, the engine may not start.

4. Pull the starter grip lightly until you feel resistance while holding the
main pipe, then pull briskly in the direction of the arrow as shown
below. Return the starter grip gently.

2. To start a cold engine, move the choke lever to the CLOSED position.
To restart warm engine, leave the choke lever in the OPEN position.

Do not use the choke if the engine is warm or the air temperature is
high.

Do not allow the starter grip to snap back against the engine. Return it
gently to prevent damage to the starter.
Damage may result if the starter grip is pulled while the engine is
running.

5. If the choke lever has been moved to the CLOSED position to start the
engine, gradually move it to the OPEN position as the engine warms
up.

11

Hot Restart

THROTTLE TRIGGER INTERLOCK

THROTTLE TRIGGER

FAS T

SLOW

ENGINE SWITCH

OFF

OFF

THROTTLE TRIGGER

SERVICING YOUR POWERHEAD

If the engine is operated at higher ambient temperatures, then turned off
and allowed to sit for a short time, it may not restart on the first pull.

If necessary, use the following procedure:

IMPORTANT SAFETY PRECAUTION

Turn the engine switch to the OFF position before performing the
following procedure. This will prevent the engine from starting and
running at maximum speed when the throttle trigger is in the FAST
speed position. If the engine starts with the throttle trigger in the FAST
speed position, the equipment can move forward rapidly or the
attachment can spin at maximum speed.

1. Turn the engine switch to the OFF position.

2. Move the choke lever to the OPEN position.

3. Hold the throttle trigger in the FAST speed position.

4. Pull the starter grip 3 to 5 times.

Follow the STARTING THE ENGINE procedure on page 11 and start the
engine with the choke lever in the OPEN position.

SETTING ENGINE SPEED

Squeeze the throttle trigger for the desired engine speed.

THE IMPORTANCE OF MAINTENANCE

Good maintenance is essential for safe, economical and trouble-free
operation. It will also help reduce pollution.

Failure to properly maintain this powerhead, or failing to
correct a problem before operation, could result in a
significant malfunction.

Some malfunctions can cause serious injuries or death.

Always follow the inspection and maintenance
recommendations and schedules in this owner's manual.

To help you properly care for your powerhead, the following pages
include a maintenance schedule, routine inspection procedures, and
simple maintenance procedures using basic hand tools. Other service
tasks that are more difficult, or require special tools, are best handled by
professionals and are normally performed by a Honda technician or other
qualified mechanic.

The maintenance schedule applies to normal operating conditions.
If you operate your powerhead under severe conditions, such as
sustained high-load or high-temperature operation, or use in unusually
wet or dusty conditions, consult your Honda servicing dealer for
recommendations applicable to your individual needs and use.

STOPPING THE ENGINE

1. Release the throttle trigger.

2. Move the engine switch to the OFF position.

Maintenance, replacement, or repair of the emission control devices
and systems may be performed by any powerhead repair
establishment or individual, using parts that are ‘‘certified’’ to EPA
standards.

MAINTENANCE SAFETY

Some of the most important safety precautions follow. However, we
cannot warn you of every conceivable hazard that can arise in
performing maintenance. Only you can decide whether or not you
should perform a given task.

Improper maintenance can cause an unsafe condition.

Failure to properly follow maintenance instructions and
precautions can cause serious injuries or death.

Always follow the procedures and precautions in this
owner’s manual.

12

SAFETY PRECAUTIONS

• Make sure the powerhead is off before you begin any maintenance or
repairs. To prevent unintentional startup, disconnect the spark plug
cap. This will eliminate several potential hazards:
– Carbon monoxide poisoning from engine exhaust.

Operate outside, away from open windows or doors.

– Burns from hot parts.

Let the engine and exhaust system cool before touching.

– Injury from moving parts.

Do not run the engine unless instructed to do so.

• Read the instructions before you begin, and make sure you have the
tools and skills required.

• To reduce the possibility of fire or explosion, be careful when working
around gasoline. Use only a non-flammable solvent, not gasoline, to
clean parts. Keep cigarettes, sparks and flames away from all fuel
related parts.

Remember that an authorized Honda servicing dealer knows your
powerhead best and is fully equipped to maintain and repair it.
To ensure the best quality and reliability, use only new Honda Genuine
parts or their equivalents for repair and replacement.

MAINTENANCE SCHEDULE

REGULAR SERVICE PERIOD (1)

Perform at every indicated month

or operating hour interval,

ITEM

Engine oil Check level o 14

Air cleaner Check o 16

Spark plug Check-adjust o

Throttle cable Check

Throttle trigger Check

Engine cooling fins Check Clean o

Shoulder harness
quick-release

Set pin knob Check o 8

Joint knob Check o 8

Around the joint
holder

Nuts, bolts, fasteners Ch eck

Spark arrester
(applicable types)

Fuel tank Clean o 18

Fuel filter Clean o 18

Clutch shoes Check o (2) –

Idle speed Check-adjust o (2) –

Valve clearance Check-adjust o (2) –

Timing belt Check After every 300 hrs. (2) (4) –

Combustion
chamber

Fuel tubes Check Every 2 years (Replace if necessary) (2) –

Oil tube Check Every 2 years (Replace if necessary) (2) –

whichever comes first.

Change o o 15

Clean o (3) 16

Replace o

Check

Check

(Retighten if
necessary)

Check Clean

Clean

Each

First

Every 3

Every 6

Every

use

month

months

or

10 hrs.

o16

o17

o8

o8

o10

months

or

25 hrs.

or

50 hrs.

Every 300 hrs. (2) –

Every 2

year

years

or

100 hrs.

or

300 hrs.

o19

Refer

to Page

17

18

(1) For professional commercial use, log hours of operation to

determine proper maintenance intervals.

(2) These items should be serviced by your servicing dealer, unless you

have the proper tools and are mechanically proficient.

Refer to the Honda shop manual for service procedures.

(3) Service more frequently when used in dusty areas.

(4) Check that there is no crack and abnormal wear-out in the belt, and

replace if it is abnormal.

Failure to follow this maintenance schedule could result in
non-warrantable failures.

13

REFUELING

FUEL TANK CAP

FUEL TANK

UPPER FUEL
LIMIT LEVEL

AMBIENT TEMPERATURE

Recommended Fuel

This engine is certified to operate on unleaded gasoline with a pump
octane rating of 86 or higher.

Refuel in a well ventilated area with the engine stopped. If the engine has
been running, allow it to cool first. Never refuel the engine inside a
building where gasoline fumes may reach flames or sparks.

You may use unleaded gasoline containing no more than 10% ethanol
(E10) or 5% methanol by volume. In addition, methanol must contain
cosolvents and corrosion inhibitors. Use of fuels with content of ethanol
or methanol greater than shown above may cause starting and/or
performance problems. It may also damage metal, rubber, and plastic
parts of the fuel system. Engine damage or performance problems that
result from using a fuel with percentages of ethanol or methanol greater
than shown above are not covered under the Warranty.

If your equipment will be used on an infrequent or intermittent basis,
please refer to the ‘‘Fuel’’ section of the ‘‘STORING YOUR POWERHEAD’’
chapter (see page 20) for additional information regarding fuel
deterioration.

Never use gasoline that is stale, contaminated, or mixed with oil. Avoid
getting dirt or water in the fuel tank.

To refuel, rest the engine a level surface with the fuel tank cap facing up,
as shown. Remove the fuel tank cap, and fill the tank with gasoline to the
bottom of the filler neck. Refuel carefully to avoid spilling fuel. Do not
overfill. There should be no fuel in the filler neck. After refueling, tighten
the fuel tank cap securely.

Keep gasoline away from appliance pilot lights, barbecues, electric
appliances, power tools, etc.

Spilled fuel is not only a fire hazard, it causes environmental damage.
Wipe up spills immediately.

ENGINE OIL

Oil is a major factor affecting performance and service life.
Use 4-stroke automotive detergent oil.

Recommended Oil

Use 4-stroke motor oil that meets or exceeds the requirements for API
service classification SJ or later (or equivalent). Always check the API
service label on the oil container to be sure it includes the letters SJ or
later (or equivalent).

Gasoline is highly flammable and explosive.

You can be burned or seriously injured when handling fuel.

• Stop the engine and let it cool before handling fuel.

• Keep heat, sparks, and flame away.

• Handle fuel only outdoors.

• Keep away from your vehicle.

• Wipe up spills immediately.

Fuel can damage paint and some types of plastic. Be careful not to spill fuel
when filling your fuel tank. Damage caused by spilled fuel is not covered
under the Distributor's Limited Warranty (U.S.) / Distributor's Warranty (CA.).

1. Check the fuel level by looking through the translucent fuel tank.

2. If the fuel level is low, refuel in a well-ventilated area with the engine

stopped. If the engine has been running, allow it to cool.

SAE 10W-30 is recommended for general use. Other viscosities shown in
the chart may be used when the average temperature in your area is
within the indicated range.

Oil Level Check

Check the engine oil level before each use, or every 10 hours if operated
continuously.

Check the engine oil level with the engine stopped and in a level
position.

1. Remove the engine oil filler cap and wipe it clean.

2. Check the oil level. If it is below the oil filler opening, fill with the
recommended oil to the oil filler opening. Do not overfill.

14

3. Reinstall the engine oil filler cap and tighten securely.

OIL FILLER OPENING

ENGINE OIL
FILLER CAP

UPPER LIMIT

OIL FILLER NECK

FUEL TANK CAP

OIL FILLER NECK

OIL FILLER OPENING

ENGINE OIL
FILLER CAP

UPPER LIMIT

OIL FILLER NECK

4. With the powerhead in a level position, fill to the bottom edge of the
oil fill hole with the recommended oil (see page 14).

Engine oil capacities
UMC425: 2.7 oz (0.08 L, 2.82 fl Imp oz)
UMC435: 3.3 oz (0.10 L, 3.52 fl Imp oz)

Some oil will remain in the powerhead after draining. When refilling
with fresh oil. Slowly add enough oil to fill to the bottom edge of the
oil fill hole as shown below. Do not overfill.

Running the engine with a low or excessive oil level can cause engine
damage. This type of damage is not covered under the Distributor's
Limited Warranty (U.S.) / Distributor's Warranty (CA.).

Running the engine with a low oil level can cause engine damage.
This type of damage is not covered under the Distributor's Limited Warranty
(U.S.) / Distributor's Warranty (CA.).

Oil Change

Drain the used oil when the engine is warm. Warm oil drains quickly and
completely.

1. Check that the fuel tank cap is tightened securely.

2. Place a suitable container below the powerhead to catch the used oil.

3. Remove the engine oil filler cap and drain the oil into the container
by tipping the powerhead toward the oil filler neck.

Please dispose of used motor oil in a manner that is compatible with
the environment. We suggest you take used oil in a sealed container to
your local recycling center or service station for reclamation. Do not
throw it in the trash, pour it on the ground, or pour it down a drain.

5. Reinstall the engine oil filler cap securely. If any oil is spilled, make
sure to wipe it up.

Wash your hands with soap and water after handling used oil.

15

AIR CLEANER

AIR CLEANER ELEMENT

CHOKE LEVER

LOWE R TABS

AIR CLEANER COVER

UPPER TAB

Squeeze and dry SqueezeDip in oilClean

Do not twist. Do not twist.

UPPER TAB

AIR CLEANER COVER

LOWE R TABS CHOKE LEVER

THROTTLE LEVER

FIXING NUT

FREE PLAY:

0.02

–0.10 in

(0.5

–2.5 mm)

TIP OF THE THROTTLE CABLE

THROTTLE CABLE

ADJUSTING NUT

Pull out
lightly

A dirty air cleaner will restrict air flow to the carburetor, reducing engine
performance. If you operate the powerhead in very dusty areas, clean the
air filter element more often than specified in the MAINTENANCE
SCHEDULE.

Operating the engine without an air filter element, or with a damaged air
filter element, will allow dirt to enter the engine, causing rapid engine wear.
This type of damage is not covered under the Distributor's Limited Warranty
(U.S.) / Distributor's Warranty (CA.).

Inspection

1. Move the choke lever to the CLOSED (upwards) position.

2. Remove the air cleaner cover by unhooking the upper tab on the top
of the air cleaner cover and its two lower tabs.

2. Reinstall the air cleaner element.

3. Reinstall the air cleaner cover by inserting the lower tabs, then insert
the upper tab.

THROTTLE CABLE

Check and Adjustment

Adjust the throttle cable free play properly.

3. Check the air cleaner element for deterioration, damage, dirt or
obstruction. Clean the air cleaner element, if it is dirty or replace it if it
is damaged.

4. Reinstall the air cleaner element. Make sure it is properly positioned
and seated against the air cleaner case.

5. Reinstall the air cleaner cover by inserting the lower tabs, then insert
the upper tab.

Free Play Inspection

1. Move the choke lever to the CLOSED (upwards) position.

2. Remove the air cleaner cover by unhooking the upper tab on the top
of the air cleaner cover and its two lower tabs.

3. Pull out the throttle cable lightly and turn the adjusting nut to adjust
the extended length of the throttle cable at the end of the cable to

0.02–0.10 in (0.5–2.5 mm). (Take care not to damage the throttle
cable.)

Cleaning

1. Clean in warm soapy water, rinse and allow to dry thoroughly. Or use
a high flash point solvent, allow to dry. Dip the element in clean
engine oil and squeeze out all the excess.
The engine will smoke during initial startup if too much oil is left in
the foam.

Do not install a dry air filter without any oil applied. Doing so will allow
dust to enter the engine, resulting in rapid engine wear, which is not
covered under the Distributor's Limited Warranty (U.S.) / Distributor's
Warranty (CA.) .

16

4. Tighten the throttle cable fixing nut securely.

5. Operate the throttle system several times and check if it has free play

THROTTLE TRIGGER INTERLOCK

THROTTLE TRIGGER

TOP COVER

SOCKET BOLT

SPARK PLUG WRENCH

SPARK PLUG

SIDE ELECTRODE

0.024–0.028 in
(0.6–0.7 mm)

SEALING WASHER

(i.e. throttle trigger does not move while operating the throttle
trigger interlock).

After adjustment, check the throttle trigger for smooth operation.
Consult your authorized Honda dealer if necessary.

6. Reinstall the air cleaner cover by inserting the lower tabs, then insert
the upper tab.

SPARK PLUG

Recommended Spark Plug: CMR5H (NGK)

2. Disconnect the spark plug cap, and remove any dirt from around the
spark plug area.

3. Remove the spark plug with a 5/8-inch spark plug wrench.

4. Inspect the spark plug.
Replace it if damaged or badly fouled, if the sealing washer is in poor
condition, or if the electrode is worn.

5. Measure the spark plug electrode gap with a wire-type feeler gauge.
Correct the gap, if necessary, by carefully bending the side electrode.
The gap should be:

0.024–0.028 in (0.6–0.7 mm)

The recommended spark plug has the correct heat range for normal
engine operating temperatures.

An incorrect spark plug can cause engine damage.

For good performance, the spark plug must be properly gapped and free
of deposits.

Do not operate the engine when the top cover is removed.

Do not pull the recoil starter handle when the top cover is
removed.

You may be injured from the rotating parts or burned by the
muffler or other engine components.

1. Loosen the socket bolt with a hexagon wrench, then remove the top
cover.

6. Install the spark plug carefully, by hand, to avoid cross-threading.

7. After the spark plug is seated, tighten with a 5/8-inch spark plug
wrench to compress the sealing washer.

When installing a new spark plug, tighten 1/2 turn after the spark
plug seats to compress the washer.

When reinstalling the original spark plug, tighten 1/8–1/4 turn after
the spark plug seats to compress the washer.

A loose spark plug can overheat and damage the engine. Overtightening
the spark plug can damage the threads in the cylinder head.

TORQUE: 11.8 Nm (1.2 kgf∙m, 8.7 lbf∙ft)

8. Attach the spark plug cap to the spark plug.

9. Install the top cover, and tighten the socket bolt securely with a
hexagon wrench.

17

COOLING FINS

COOLING FINS
(Inside the top cover)

SOCKET BOLT

TOP COVER

ENGINE OIL FILLER CAP

FUEL FILLER NECK

FUEL TANK CAP

FUEL FILTER

FUEL TUBES

Inspection

1. Loosen the socket bolt, then remove the top cover.

2. Inspect the engine cooling fins, and clean out debris if necessary.

3. Install the top cover, and tighten the socket bolt securely.

3. Pull out the fuel filter with the mechanic’s wire from the fuel filler
neck gently.

4. Inspect the fuel filter. If the fuel filter is dirty, wash it gently with non­flammable or high flash point solvent. If the fuel filter is excessively
dirty, replace it.

FUEL FILTER AND FUEL TANK

Fuel filter inspection and Fuel tank cleaning

Gasoline is highly flammable and explosive.

You can be burned or seriously injured when handling fuel.

• Stop the engine and let it cool before handling fuel.

• Keep heat, sparks, and flame away.

• Handle fuel only outdoors.

• Keep away from your vehicle.

• Wipe up spills immediately.

1. Check that the engine oil filler cap is tightened securely.

2. Remove the fuel tank cap, and drain the fuel into an approved
gasoline container by tipping the powerhead toward the fuel filler
neck.

5. Remove water and dirt from the fuel tank by rinsing the inside of the
fuel tank with non-flammable or high flash point solvent.

6. Insert the fuel filter into the fuel tank and tighten the fuel tank cap
securely.

FUEL TUBE

Inspection

Check fuel tubes for cracks and any other deterioration and confirm that
there is no leakage of fuel on the fuel tubes. If you notice any abnormal
symptoms on the fuel tubes, contact your servicing dealer.

18

SPARK ARRESTER (applicable types)

SOCKET BOLT

TOP COVER

SPARK PLUG

MUFFLER

4×6 mm
SELF-TAPPING
SCREWS
(UMC435 [3])
(UMC425 [2])

SPARK ARRESTER’S
OUTLET

SPARK ARRESTER

EXHAUST FILTER
(UMC435 only)

(UMC435 only)

EXHAUST FILTER

SPARK ARRESTER SCREEN

The spark arrester must be serviced every 100 hours to keep it
functioning as designed.
If the engine has been running, the muffler will be hot. Allow it to cool
before servicing the spark arrester.

Spark Arrester Removal

1. Loosen the socket bolt, then remove the top cover.

2. Remove the 4×6 mm self-tapping screws from the spark arrester, and
remove the spark arrester and exhaust filter (UMC435 only) from the
muffler.

Spark Arrester Cleaning & Inspection

1. Use a brush to remove carbon deposits from the spark arrester
screen. Be careful to avoid damaging the screen.

The spark arrester must be free of breaks and holes. Replace the spark
arrester if it is damaged.

2. Install the exhaust filter (UMC435 only) and spark arrester in the
reverse order of disassembly.

When you install the spark arrester, the spark arrester’s outlet must
point the opposite side of the spark plug.

3. Install the top cover, and tighten the socket bolt securely.

Exhaust Filter Cleaning & Inspection (UMC435 only)

Pinch the exhaust filter, and strike it lightly with a finger, to remove
carbon deposits. Be careful not to strike it too hard. The exhaust filter
must be free of breaks and holes. If it is damaged or fouled excessively,
replaced it.

19

HELPFUL TIPS & SUGGESTIONS

ENGINE OIL FILLER CAP

FUEL FILLER NECK

FUEL TANK CAP

FUEL RETURN TUBE

FUEL TANK CAP

PRIMING PUMP

Short Term Storage (30–90 days)

STORING YOUR POWERHEAD

Storage Preparation

Proper storage preparation is essential for keeping your powerhead
trouble-free and looking good. The following steps will help to keep rust
and corrosion from impairing your powerhead’s function and
appearance, and will make the engine easier to start when you use it
again.

Cleaning

If the engine has been running, allow it to cool for at least half an hour
before cleaning. Clean all exterior surfaces, touch up any damaged paint,
and coat other areas that may rust with a light film of oil.

Using a garden hose or pressure washing equipment can force water into the
air cleaner or muffler opening. Water in the air cleaner will soak the air filter,
and water that passes through the air filter or muffler can enter the cylinder,
causing damage.

Fuel

Depending on the region where you operate your equipment, fuel
formulations may deteriorate and oxidize rapidly. Fuel deterioration and
oxidation can occur in as little as 30 days and may cause damage to the
carburetor and/or fuel system. Please check with your servicing dealer for
local storage recommendations.

Adding a Gasoline Stabilizer to Extend Fuel Storage Life

When adding a gasoline stabilizer, fill the fuel tank with fresh gasoline. If
only partially filled, air in the tank will promote fuel deterioration during
storage. If you keep a container of gasoline for refueling, be sure that it
contains only fresh gasoline.

1. Add gasoline stabilizer following the manufacturer’s instructions.

2. After adding a gasoline stabilizer, run the engine outdoors for 10
minutes to be sure that treated gasoline has replaced the untreated
gasoline in the carburetor.

3. Stop the engine.

Long Term or Seasonal Storage (greater than 90 days)

Draining the Fuel Tank and Carburetor

Gasoline is highly flammable and explosive.

You can be burned or seriously injured when handling fuel.

•

Stop the engine and let it cool before handling fuel.

•

Keep heat, sparks, and flame away.

• Handle fuel only outdoors.

• Keep away from your vehicle.

• Wipe up spills immediately.

1. Make sure the engine oil filler cap is tightened securely.

Gasoline will oxidize and deteriorate in storage. Deteriorated gasoline
will cause hard starting, and it leaves gum deposits that clog the fuel
system. If the gasoline in your powerhead deteriorates during storage,
you may need to have the carburetor and other fuel system components
serviced or replaced.
The length of time that gasoline can be left in your fuel tank and
carburetor without causing functional problems will vary with such
factors as gasoline blend, your storage temperatures, and whether the
fuel tank is partially or completely filled. The air in a partially filled fuel
tank promotes fuel deterioration. Very warm storage temperatures
accelerate fuel deterioration. Fuel deterioration problems may occur
within a few months, or even less if the gasoline was not fresh when you
filled the fuel tank.

Fuel system damage or engine performance problems resulting from
neglected storage preparation are not covered under the Distributor's
Limited Warranty (U.S.) / Distributor's Warranty (CA.).

You can extend fuel storage life by adding a gasoline stabilizer that is
formulated for that purpose, or you can avoid fuel deterioration
problems by draining the fuel tank and carburetor.

2. Remove the fuel tank cap and drain the fuel into an approved
gasoline container by tipping the powerhead toward the fuel filler
neck.

3. Press the priming pump several times until all fuel has returned to the
fuel tank.

20

4. Tip the powerhead toward the fuel filler neck again to drain the fuel.

CARRYING HARNESS

MAIN PIPE

TRANSPORTING

5. After all fuel has drained, reinstall the fuel tank cap securely.

Engine Oil

1. Change the engine oil (see page 15).

2. Clean the air cleaner (see page 16).

3. Loosen the socket bolt, then remove the top cover (see page 17).

4. Remove the spark plug (see page 17).

5. Apply a couple of drops of clean engine oil into the cylinder.

6. Install the top cover temporarily.

7. Pull the starter grip several times to distribute the oil in the cylinder.

8. Remove the top cover, then reinstall the spark plug.

9. Install the top cover, and tighten the socket bolt securely.

10. Pull the starter grip slowly until resistance is felt.

11. Move the choke lever to the CLOSED position (see page 6).

12. Cover the powerhead and store in a dry, dust-free area.

Storage Precautions

If the engine has been running, allow it to cool for at least 15 minutes
before loading the powerhead on the transport vehicle. A hot engine and
exhaust system can burn you and can ignite some materials.

Always turn the engine switch to the OFF position. Make sure the fuel cap
is securely tightened.
Carrying the powerhead by hand:
Attach it to the carrying harness or hold the main pipe to carry it with
good balance.

Transporting the powerhead by vehicle:
Secure the powerhead. Make sure it will not move or fall down.

If your powerhead will be stored with gasoline in the fuel tank and
carburetor, it is important to reduce the hazard of gasoline vapor
ignition. Select a well ventilated storage area away from any appliance
that operates with a flame, such as a furnace, water heater, or clothes
dryer. Also avoid any area with a spark-producing electric motor, or
where power tools are operated.

If possible, avoid storage areas with high humidity, because that
promotes rust and corrosion.

Keep the powerhead level in storage. Tilting can cause fuel or oil leakage.

With the engine and exhaust system cool, cover the powerhead to keep
out dust. A hot engine and exhaust system can ignite or melt some
materials. Do not use a plastic sheet as a dust cover. A nonporous cover
will trap moisture around the powerhead, promoting rust and corrosion.

Removal from Storage

Check your powerhead as described in the BEFORE OPERATION CHECKS
section of this manual (see page 7).

If the fuel was drained during storage preparation, fill the tank with fresh
gasoline. If you keep a container of gasoline for refueling, be sure it
contains only fresh gasoline. Gasoline oxidizes and deteriorates over
time, causing hard starting.

If the cylinder was coated with oil during storage preparation, the engine
will smoke briefly at startup. This is normal.

21

TAKING CARE OF UNEXPECTED PROBLEMS

ENGINE SERIAL NUMBER

FRAME SERIAL NUMBER

TECHNICAL & CONSUMER INFORMATION

ENGINE WILL NOT START

Possible Cause Correction

Choke open. Move lever to CLOSED position

unless the engine is warm.

Engine switch OFF. Turn engine switch to ON position.

Out of fuel. Refuel (p. 14).

Bad fuel; powerhead stored
without treating or draining
gasoline, or refueled with bad
gasoline.

Spark plug faulty, fouled, or
improperly gapped.

Spark plug wet with fuel (flooded
engine).

Fuel filter restricted, carburetor
malfunction, ignition malfunction,
valves stuck, etc.

ENGINE LACKS POWER

Possible Cause Correction

Filter element restricted. Clean or replace filter element (p.

Bad fuel; powerhead stored
without treating or draining
gasoline, or refueled with bad
gasoline.

Fuel filter restricted, carburetor
malfunction, ignition malfunction,
valves stuck, etc.

Drain fuel tank and carburetor (p.

20). Refuel with fresh gasoline (p.

14).

Gap or replace spark plug (p. 17).

Allow the spark plug to dry.
After drying, install the spark plug
and start the engine (p. 11).

Take powerhead to your servicing
dealer, or refer to shop manual.

16).

Drain fuel tank and carburetor (p.

20). Refuel with fresh gasoline (p.

14).

Take powerhead to your servicing
dealer, or refer to shop manual.

TECHNICAL INFORMATION

Serial Number Location

Record the engine and frame serial numbers in the spaces below. You
will need these serial numbers when ordering parts and when making
technical or warranty inquiries.

Engine serial number:

Frame serial number:

Date Purchased: / /

22

Carburetor Modifications for High Altitude Operation

At high altitude, the standard carburetor air-fuel mixture will be too rich.
Performance will decrease, and fuel consumption will increase. A very
rich mixture will also foul the spark plug and cause hard starting.
Operation at an altitude that differs from that at which this engine was
certified, for extended periods of time, may increase emissions.

High altitude performance can be improved by specific modifications to
the carburetor. If you always operate your powerhead at altitudes above
2,000 feet (610 meters), have your servicing dealer perform this
carburetor modification. This engine, when operated at high altitude
with the carburetor modifications for high altitude use, will meet each
emission standard throughout its useful life.

Even with carburetor modification, engine horsepower will decrease
about 3.5% for each 1,000-foot (300-meter) increase in altitude. The
effect of altitude on horsepower will be greater than this if no carburetor
modification is made.

When the carburetor has been modified for high altitude operation, the air­fuel mixture will be too lean for low altitude use. Operation at altitudes below
2,000 feet (610 meters) with a modified carburetor may cause the engine to
overheat and result in serious engine damage. For use at low altitudes, have
your servicing dealer return the carburetor to original factory specifications.

Emission Control System Information

Source of Emissions

The combustion process produces carbon monoxide, oxides of nitrogen,
and hydrocarbons. Control of hydrocarbons and oxides of nitrogen is
very important because, under certain conditions, they react to form
photochemical smog when subjected to sunlight. Carbon monoxide
does not react in the same way, but it is toxic.

Problems That May Affect Emissions

If you are aware of any of the following symptoms, have your engine
inspected and repaired by your authorized Honda Power Equipment
dealer.

• Hard starting or stalling after starting.

•Rough idle.

• Misfiring or backfiring under load.

• Afterburning (backfiring).

• Black exhaust smoke or high fuel consumption.

Replacement Parts

The emissions control systems on your new Honda engine were designed, built, and
certified to conform with EPA, California (models certified for sale in California only),
and Canadian emissions regulations. We recommend the use of Honda Genuine parts
whenever you have maintenance done. These original-design replacement parts are
manufactured to the same standards as the original parts, so you can be confident of
their performance. Honda cannot deny coverage under the emission warranty solely
for the use of non-Honda replacement parts or service performed at a location other
than an authorized Honda dealership; you may use comparable EPA certified parts,
and have service performed at non- Honda locations. However, the use of
replacement parts that are not of the original design and quality may impair the
effectiveness of your emissions control system.

A manufacturer of an aftermarket part assumes the responsibility that the part will
not adversely affect emissions performance. The manufacturer or rebuilder of the
part must certify that use of the part will not result in a failure of the engine to
comply with emissions regulations.

Maintenance

As the power equipment engine owner, you are responsible for completing all
required maintenance listed in your owner's manual. Honda recommends that
you retain all receipts covering maintenance on your power equipment
engine, but Honda cannot deny warranty coverage solely for the lack of
receipts or for your failure to ensure that all scheduled maintenance has been
completed.

Honda utilizes appropriate air/fuel ratios and other emissions control
systems to reduce the emissions of carbon monoxide, oxides of nitrogen,
and hydrocarbons.

Additionally, Honda fuel systems utilize components and control
technologies to reduce evaporative emissions.

The U.S. and California Clean Air Acts, and Environment and Climate
Change Canada (ECCC)

U.S. EPA, California and Canadian regulations require all manufacturers to
furnish written instructions describing the operation and maintenance of
emission control systems.

The following instructions and procedures must be followed in order to
keep the emissions from your Honda engine within the emission
standards.

Tampering and Altering

Tampering is a violation of Federal and California law.

Tampering with or altering the emission control system may increase
emissions beyond the legal limit. Among those acts that constitute
tampering are:

• Removal or alteration of any part of the intake, fuel, or exhaust
systems.

• Alterations that would cause the engine to operate outside its design
parameters.

Follow the MAINTENANCE SCHEDULE on page 13. Remember that this
schedule is based on the assumption that your Honda engine product
will be used for its designed purpose. Sustained high-load or high­temperature operation, or use in dusty conditions, will require more
frequent service.

Air Index
(Models certified for sale in California)

An Air Index Information hang tag/label is applied to engines certified to
an emission durability time period in accordance with the requirements
of the California Air Resources Board.

The bar graph is intended to provide you, our customer, the ability to
compare the emissions performance of available engines. The lower the
Air Index, the less pollution.

The durability description is intended to provide you with information
relating to the engine’s emission durability period. The descriptive term
indicates the useful life period for the engine’s emission control system.
See your Emission Control System Warranty (see page 24) for additional
information.

Descriptive Term Applicable to Emissions Durability Period

Moderate 50 hours (0–80 cc, inclusive)

125 hours (greater than 80 cc)

Intermediate 125 hours (0–80 cc, inclusive)

250 hours (greater than 80 cc)

Extended 300 hours (0–80 cc, inclusive)

500 hours (greater than 80 cc)
1,000 hours (225 cc and greater)

The Air Index Information hang tag/label must remain on the powerhead until it is
sold. Remove the hang tag before operating the powerhead.

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Emission Control System Warranty

Your Honda Power Equipment engine is designed, built, and equipped to meet the
U.S. EPA, Environment Canada, and California Air Resources Board (models certified
for sale in California only) emission standard for spark ignited engines. American
Honda Motor provides the emission warranty coverage for engines in the United
States and its territories. Honda Canada provides the emission warranty for engines
in the 13 provinces and territories of Canada.

Warra nty Cove rage

Honda Power Equipment engines certified to the U.S. EPA, Environment
Canada, and State of California (models certified for sale in California
only) emission regulations are covered by this warranty to be free from
defects in materials and workmanship that may keep it from meeting the
applicable U.S. EPA, CARB and Canadian emissions requirements for a
minimum of 2 years or the length of the Honda Power Equipment
Distributor’s Limited Warranty, whichever is longer, from the original date
of delivery to the retail purchaser. This warranty is transferable to each
subsequent purchaser for the duration of the warranty period. Warranty
repairs will be made without charge for diagnosis, parts, and labor.
Information about how to make a warranty claim, as well as a description
of how a claim can be made and/or how service can be provided, can be
obtained by contacting an authorized Honda Power Equipment dealer or
by contacting the following:

American Honda

Email: [email protected]
Telephone: [phone]

Honda Canada

Telephone: [phone]

The covered components include all components whose failure would
increase an engine's emissions of any regulated pollutant or evaporative
emissions. A list of specific components can be found in the separately
included emissions warranty statement.

Specific warranty terms, coverage, limitations, and manner of seeking
warranty service are also set forth in the separately included emissions
warranty statement. In addition, the emission warranty statement can
also be found on the Honda Power equipment website or at the
following link:
http://powerequipment.honda.com/support/warranty

24

Specifications

MODEL UMC425 UMC435

Description code HAGT HALT HAHT HAMT

Type LAAT

LACT, LAC1

LAAT

LACT, LAC1

Frame

MODEL UMC425 UMC435

Handle type Loop

Clutch type Centrifugal clutch

Overall length 44.7 in (1,135 mm) 45.1 in (1,145 mm)

Overall width 12.4 in (315 mm) 12.6 in (320 mm)

Overall height 9.6 in (245 mm) 10.0 in (255 mm)

Dry mass (weight) 11.2 lbs (5.1 kg) 13.2 lbs (6.0 kg)

Engine

MODEL UMC425

Engine model GX25T

Engine description code GCALT

Engine type 4-stroke, overhead cam, single cylinder

Displacement

1.5 cu-in (25.0 cm3)

Bore x Stroke 1.4 × 1.0 in (35.0 × 26.0 mm)

Idle speed 3,100 ± 200 rpm

Maximum no load engine

MIN. 10,000 rpm

speed

Cooling system Forced air

Ignition system Transistor magneto

Engine oil capacity 2.7 oz (0.08 L, 2.82 fl Imp oz)

Fuel tank capacity 0.14 US gal (0.53 L, 18.7 fl Imp oz)

Spark plug CMR5H (NGK)

Tuneup Specifications

ITEM SPECIFICATION MAINTENANCE

Spark plug gap 0.024–0.028 in

Refer to page: 17

(0.6–0.7 mm)

Idle speed 3,100±200 rpm See your servicing

Valve clearance
(cold)

Other

IN: 0.08±0.02 mm
EX: 0.11±0.02 mm

No other adjustments needed.

dealer

specifications

Quick Reference Information

Fuel Regular unleaded gasoline with an ethanol content

of no more than 10% and a pump octane rating of
86 or higher (see page 14).

Engine oil SAE 10W-30, API SJ or later, for general use.

Include capacities:
UMC425: 2.7 oz (0.08 L, 2.82 fl Imp oz)
UMC435: 3.3 oz (0.10 L, 3.52 fl Imp oz)
Refer to page 14.

Spark plug CMR5H (NGK)

Maintenance Before each use:

• Check engine oil level. Refer to page 14.

• Check air filter. Refer to page 16.

First 10 hours:
Change engine oil. Refer to page 15.

Subsequent:
Refer to the maintenance schedule on page 13.

Engine

MODEL UMC435

Engine model GX35T

Engine description code GCAMT

Engine type 4-stroke, overhead cam, single cylinder

Displacement

2.18 cu-in (35.8 cm

3

)

Bore x Stroke 1.5 × 1.2 in (39.0 × 30.0 mm)

Idle speed 3,100 ± 200 rpm

Maximum no load engine

MIN. 10,000 rpm

speed

Cooling system Forced air

Ignition system Transistor magneto

Engine oil capacity 3.3 oz (0.10 L, 3.52 fl Imp oz)

Fuel tank capacity 0.17 US gal (0.63 L, 22.2 fl Imp oz)

Spark plug CMR5H (NGK)

Specifications may vary according to the types, and are subject to change
without notice.

25

CONSUMER INFORMATION

Customer Service Information (For USA and Canada)

Dealer Locator Information

To find an authorized Honda Servicing Dealer
For USA:
Visit our website: http://powerequipment.honda.com/dealer-locator
For Canada:
Call 1-888-946-6329 or visit our website:
English
http://powerequipment.honda.ca/dealerlocator
French
http://powerequipment.honda.ca/trouver-concessionaire

Honda Publications (For USA and Canada)

Shop Manual

This manual covers complete maintenance and overhaul procedures.
It is intended to be used by a skilled technician.
For USA:
Available through your Honda dealer or visit
http://powerequipment.honda.com/support/shop-manuals
For Canada:
Contact your dealer for information on the Shop Manual.

Parts Catalog

For USA:
This manual provides complete, illustrated parts lists. Available through
your Honda dealer.
For Canada:
Contact your dealer for information on parts.

Accessories Catalog

Your authorized Honda power equipment dealer offers a selection of
accessories (optional equipment) to make your Powerhead even more
useful.
For USA:
Visit http://powerequipment.honda.com/trimmers/accessories
and click on see all powerhead accessories to see the entire catalog of
accessories.
For Canada:
Check with your dealer or visit www.honda.ca and select the Accessories
tab under the Powerhead segment to view the range of accessories
available for your model.

Honda Power Equipment dealership personnel are trained professionals.
They should be able to answer any question you may have. If you
encounter a problem that your dealer does not solve to your satisfaction,
please discuss it with the dealership’s management. The Service Manager
or General Manager can help. Almost all problems are solved in this way.

If you are dissatisfied with the decision made by the dealership's
management, contact the Honda Power Equipment Customer Relations
Office. You can write to:

American Honda Motor Co., Inc.

Power Equipment Division

Customer Relations Office

4900 Marconi Drive

Alpharetta, Georgia 30005 – 8847

Telephone: [phone]

9:00 am to 7:30 pm ET

In Canada:

Honda Canada, Inc.

Customer Relation Department

180 Honda Boulevard

Markham, Ontario L6C 0H9

Tel: [phone] (Toll free)

Fax: [phone] (Toll free)

E-mail: [email protected]

When you write or call, please give us this information:

• Model and serial numbers (see page 22)

• Name of the dealer who sold the Powerhead to you

• Name and address of the dealer who services your Powerhead

• Date of purchase

• Your name, address, and telephone number

• A detailed description of the problem

26