Zenoah BT251 Owner's manual

OWNER/OPERATOR MANUAL
LINE TRIMMER
848-J25-93A1 (704)
The engine exhaust from this product
contains chemicals known to the State
of California to cause cancer, birth
defects or other reproductive harm.
WARNING
Before using our products, please
read this manual carefully to
understand the proper use of your
unit.
WARNING
BT251

SAFETY FIRST
Instructions contained in warnings within this
manual marked with a symbol concern
critical points which must be taken into
consideration to prevent possible serious
bodily injury, and for this reason you are
requested to read all such instructions
carefully and follow them without fail.
■WARNINGS IN THE MANUAL
This mark indicates instructions which must be
followed in order to prevent accidents which could
lead to serious bodily injury or death.
This mark indicates instructions which must be
followed, or it leads to mechanical failure,
breakdown, or damage.
This mark indicates hints or directions useful in the
use of the product.
NOTE
IMPORTANT
WARNING
CONTENTS
1. Parts location …………………………………3
2. Specifications …………………………………3
3. Warning labels on the machine ……………4
4. Symbols on the machine ……………………4
5. For safe operation ……………………………5
6. Set up…………………………………………11
7. Fuel……………………………………………12
8. Operation ……………………………………14
9. Maintenance …………………………………17
10. Storage ………………………………………22
11. Troubleshooting guide………………………22
12. Disposal………………………………………22
13. Limited warranty ……………………………23

2. Specifications
■BT251
Overall size(LxWxH)························································ 67.9(1725)x9.4(240)x19.5(495) in(mm)
Dry weight w/o acc.····························································································· 11.0 lbs (5.01kg)
Engine Type······················································································ Air-cooled 2-stroke gasoline
Model····················································································································· GT25N
Displacement ······················································································· 1.6cu-in (25.4cm3)
Max. output·························································································· 1.2Hp at 8500 rpm
Fuel ······················································································· Mixture(Gasoline 50 : Oil 1)
(when using ZENOAH genuine oil)
Carburetor ··················································································· Walbro Diaphragm type
Spark plug ································································································· NGK BPMR7A
Fuel tank capacity······························································································ 22.3 fl.oz (0.62)
Transmission··········································································· Centrifugal clutch, Rigid driveshaft
Reduction ratio ····················································································································· 1.000
Cutting head rotating direction······························································ Clockwise(Operator view)
Durability period····················································································································50hrs.
Standard Accessories
3.5 in. 2-line Head ····································································································· 1 pc.
Tool set·······················································································································1 set
Specifications are subject to change without notice.
1. Parts location
1. Loop handle
2. Ignition switch
3. Throttle cable
4. Throttle lever
5. Drive shaft housing
6. Debris guard
7. Cutting line head
8. Bearing case
9. Spark arrester
10. Starter knob
11. Fuel tank
12. Primer pump
13. Choke lever
14. Air cleaner cover
3

For safe operation and maintenance, symbols are
carved in relief on the machine. According to these
indications, please be careful not to make a
mistake.
(a)The port to refuel the "MIX GASOLINE"
Position: FUEL TANK CAP
(b)The direction A to close the choke
The direction B to open the choke
Position: AIR CLEANER COVER
(c) This unit is fitted with only flexible line cutter.
Never use cutting blade made of metal or
plastic.
Position: DEBRIS GUARD
4. Symbols on the machine
(1)Read owner's manual before operating machine.
(2)Wear head, eye and ear protection.
(3)Wear foot protection.
(4)Wear gloves.
(5)Beware of thrown objects.
(6)Warning / Attention
(7)Keep all children, bystanders and helpers 15 meters away from the brushcutter
If warning label peel off or become soiled and impossible to read, you should contact the dealer
from which you purchased the product to order new labels and affix them in the required
location(s).
Never modify your brushcutter.
We won't warrant the machine, if you use the remodeled brushcutter or you don't observe
the proper usage written in the manual.
WARNING
IMPORTANT
15m (50ft)
(1) (2) (3) (4) (5) (6) (7)
3. Warning labels on the machine
4

5
5. For safe operation
1. Read this manual carefully until you
completely understand and follow all safety
and operating instructions.
2. Keep this manual handy so that you may refer
to it later whenever any questions arise. Also
note, if you have any questions which cannot
be answered herein, contact the dealer from
whom you purchased the product.
3. Always be sure to include this manual when
selling, lending, or otherwise transferring the
ownership of this product.
4. Never allow children or anyone unable to fully
understand the directions given in the manual
to use the machine.
■WORKING CONDITION
1. When using the product, you should wear proper
clothing and protective equipment.
(1)Helmet
(2)Ear protectors
(3)Protection goggles or face protector
(4)Thick work gloves
(5)Non-slip-sole work boots
2. And you should carry with you.
(1)Attached tools and files
(2)Properly reserved fuel
(3)Spare blade
(4)Things to notify your working area (rope,
warning signs)
(5)Whistle (for collaboration or emergency)
(6)Hatchet or saw (for removal of obstacles)
3. Do not wear loose clothing, jewelry, short
trousers, sandals, or go barefoot. Do not wear
anything which might be caught by a moving
part of the unit. Secure hair so it is above
shoulder length.
■WORKING CIRCUMSTANCE
1. Never start the engine inside a closed room or
building. Exhaust gases contain dangerous
carbon monoxide.
2. Never use the product,
a. when the ground is slippery or when you can’t
maintain a steady posture.

6
b. At night, at times of heavy fog, or at any other
times when your field of vision might be
limited and it would be difficult to gain a clear
view of the working area.
c. During rain storms, during lightning storms, at
times of strong or gale-force winds, or at any
other times when weather conditions might
make it unsafe to use the product.
■WORKING PLAN
1. You should never use the product when under
the influence of alcohol, when suffering from
exhaustion or lack of sleep, when suffering from
drowsiness as a result of having taken cold
medicine or at any other time when a possibility
exists that your judgment might be impaired or
that you might not be able to operate the product
properly and in a safe manner.
2. When planning your work schedule, allow plenty
of time to rest. Limit the amount of time over
which the product is to be used continuously to
somewhere around 30~40 minutes per session,
and take 10~20 minutes of rest between work
sessions. Also try to keep the total amount of
work performed in a single day under 2 hours or
less.
1. If you don’t observe the working time, or
working manner (See ■USING THE
PRODUCT), Repetitive Stress Injury(RSI)
could occur.
If you feel discomfort, redness and swelling
of your fingers or any other part of your
body, see a doctor before getting worse.
2. To avoid noise complaints, in general,
operate product between 8a.m. and 5p.m. on
weekdays and 9a.m. to 5p.m. weekends.
Check and follow the local regulations as to sound
level and hours of operations for the product.
NOTE
WARNING
5. For safe operation

■BEFORE STARTING THE ENGINE
1. The area within a perimeter of 50 feet (15m) of
the person using the product should be
considered a hazardous area into which no one
should enter. If necessary yellow warning rope,
warning signs should be placed around the
perimeter of the area. When work is to be
performed simultaneously by two or more
persons, care should also be taken to constantly
look around or otherwise check for the presence
and locations of other people working so as to
maintain a distance between each person
sufficient to ensure safety.
2. Check the condition of working area to avoid any
accident by hitting hidden obstacles such as
stumps, stones, cans, or broken grass.
Remove any obstacle before beginning work.
3. Inspect the entire unit for loose fasteners and
fuel leakage. Make sure that the cutting
attachment is properly installed and securely
fastened.
4. Be sure the debris guard is firmly attached in
place.
5. If the cutting head is the metal blade, use the
shoulder strap. Adjust the strap for comfort
before starting the engine. The strap should be
adjusted so the left hand can comfortably hold
the handlebar grip approximately waist high.
■STARTING THE ENGINE
1. Keep bystanders and animals at least 50feet
(15m) away from the operating point. If you are
approached, immediately stop the engine.
2. The product is equipped with a centrifugal clutch
mechanism, so the cutting attachment begins to
rotate as soon as the engine is started by putting
the throttle into the start position. When starting
the engine, place the product onto the ground in
a flat clear area and hold it firmly in place so as
to ensure that neither the cutting part nor the
throttle come into contact with any obstacle
when the engine starts.
IMPORTANT
5. For safe operation
7

8
Never place the throttle into the high speed
position when starting the engine.
3. After starting the engine, check to make sure
that the cutting attachment stops rotating when
the throttle is moved fully back to its original
position. If it continues to rotate even after the
throttle has been moved fully back, turn off the
engine and take the unit to your authorized
ZENOAH servicing dealer for repair.
■USING THE PRODUCT
Cut only materials recommended by the
manufacturer. And use only for tasks explained
in the manual.
1. Grip the handles firmly with both hands using
your whole hand. Place your feet slightly apart
(slightly further apart than the width of your
shoulders) so that your weight is distributed
evenly across both legs, and always be sure to
maintain a steady, even posture while working.
2. Keep cutting attachment below waist level.
3. Maintain the speed of the engine at the level
required to perform cutting work, and never raise
the speed of the engine above the level
necessary.
4. If the unit start to shake or vibrate, turn off the
engine and check the whole unit. Do not use it
until the trouble has been properly corrected.
5. Keep all parts of your body away from rotating
cutting attachment and hot surfaces.
6. Never touch the muffler, spark plug, or other
metallic parts of the engine while the engine is in
operation or immediately after shutting down the
engine. Doing so could result in serious burns or
electrical shock.
IMPORTANT
WARNING
5. For safe operation

•IF SOMEONE COMES
1. Guard against hazardous situations at all times.
Warn adults to keep pets and children away
from the area. Be careful if you are approached.
Injury may result from flying debris.
2. If someone calls out or otherwise interrupts you
while working, always be sure to turn off the
engine before turning around.
■MAINTENANCE
1. In order to maintain your product in proper
working order, perform the maintenance and
checking operations described in the manual at
regular intervals.
2. Always be sure to turn off the engine before
performing any maintenance or checking
procedures.
The metallic parts reach high temperatures
immediately after stopping the engine.
3. When replacing the cutting attachment or any
other part, or when replacing the oil or any
lubricant, always be sure to use only ZENOAH
products or products which have been
certified by ZENOAH for use with the
ZENOAH product.
4. In the event that any part must be replaced or
any maintenance or repair work not described in
this manual must be performed, please contact a
representative from the store nearest ZENOAH
authorized servicing dealer for assistance.
5. Do not use any accessory or attachment other
than those bearing the ZENOAH mark and
recommended for the unit.
6. Under no circumstances should you ever take
apart the product or alter it in any way. Doing so
might result in the product becoming damaged
during operation or the product becoming unable
to operate properly.
WARNING
5. For safe operation
9

10 
5. For safe operation
■HANDLING FUEL
1. The engine of the ZENOAH product is designed
to run on a mixed fuel which contains highly
flammable gasoline. Never store cans of fuel or
refill the tank of the unit in any place where there
is a boiler, stove, wood fire, electrical sparks,
welding sparks, or any other source of heat or
fire which might ignite the fuel.
2. Never smoke while operating the unit or refilling
its fuel tank.
3. When refilling the tank, always turn off the
engine and allow it to cool down. Take a careful
look around to make sure that there are no
sparks or open flames anywhere nearby before
refueling.
4. Wipe spilled fuel completely using a dry rag if
any fuel spillage occurs during refueling.
5. After refueling, screw the fuel cap back tightly
onto the fuel tank and then carry the unit to a
spot 10feet (3m) or more away from where it
was refueled before turning on the engine.
■TRANSPORTATION
1. When hand-carrying the product, cover over the
cutting part if necessary, lift up the product and
carry it paying attention to the blade.
2. Never transport the product over rough roads
over long distances by vehicle without removing
all fuel from the fuel tank. If doing so, fuel might
leak from the tank during transport.

■INSTALLING HANDLE (SE1)
•Mount the handle to the shaft tube and clamp it
at your best operating position.
■INSTALLING DEBRIS GUARD (SE2)
•Put the debris guard on the bearing case, attach
it with the screw, washer, nut and support plate
provided.
(1) Support plate
■INSTALLING CUTTING HEAD (SE3)
1. While locking the gear shaft by inserting the
attached hexagon bar into the upper holder and
the housing.
2. Rotate the cutting head to engage threads.
Hand-tighten it securely.
6. Set up
SE1
(1)
SE2
SE3
11 

12 
7. Fuel
■RECOMMENDED MIXING RATIO
GASOLINE 50:OIL 1
(when using ZENOAH genuine oil)
•Exhaust emission are controlled by the
fundamental engine parameters and
components(eq., carburation, ignition
timing and port timing) without
addition of any major hardware or the
introduction of an inert material during
combustion.
•These engines are certified to operate on
unleaded gasoline.
•Make sure to use gasoline with a
minimum octane number of 89 RON
(USA/Canada: 87AL)
•If you use a gasoline of a lower octane
value than prescribed, there is a danger
that the engine temperature may rise and
an engine problem such as piston seizing
may consequently occur.
•Unleaded gasoline is recommended to
reduce the contamination of the air for the
sake of your health and the environment.
•Poor quality gasolines or oils may damage
sealing rings, fuel lines or fuel tank of the
engine.
■HOW TO MIX FUEL
Pay attention to agitation.
1. Measure out the quantities of gasoline
and oil to be mixed.
2. Put some of the gasoline into a clean,
approved fuel container.
3. Pour in all of the oil and agitate well.
4. Pour In the rest of gasoline and agitate
IMPORTANT
•Gasoline is very flammable. Avoid
smoking or bringing any flame or
sparks near fuel. Make sure to stop the
engine and allow it cool before
refueling the unit. Select outdoor bare
ground for fueling and move at least
3m (10ft) away from the fueling point
before starting the engine.
•The ZENOAH engines are lubricated by
oil specially formulated for air-cooled 2-
cycle gasoline engine use. If ZENOAH oil
is not available, use an anti-oxidant added
quality oil expressly labeled for air-cooled
2-cycle engine use. (JASO FC GRADE
OIL or ISO EGC GRADE)
•Do not use BIA or TCW (2-stroke water-
cooling type) mixed oil.
WARNING
50:1 MIXING CHART
GASOLINE gal. 12345
2-CYCLE OIL fl.oz 2.6 5.2 7.8 10.4 13
GASOLINE liter 12345
2-CYCLE OIL ml 20 40 60 80 100

7. Fuel
13 
again for at least one minute. As some
oils may be difficult to agitate depending
on oil ingredients, sufficient agitation is
necessary for the engine to last long. Be
careful that, if the agitation is insufficient,
there is an increased danger of early
piston seizing due to abnormally lean
mixture.
5. Put a clear indication on the outside of the
container to avoid mixing up with gasoline
or other containers.
6. Indicate the contents on outside of
container for easy identification.
■FUELING THE UNIT
1. Untwist and remove the fuel cap. Rest the
cap on a dustless place.
2. Put fuel into the fuel tank to 80% of the full
capacity.
3. Fasten the fuel cap securely and wipe up
any fuel spillage around the unit.
1. Select bare ground for fueling.
2. Move at least 10feet (3meters) away from
the fueling point before starting the
engine.
3. Stop the engine before refueling the unit.
At that time, be sure to sufficiently agitate
the mixed gasoline in the container.
FOR YOUR ENGINE LIFE, AVOID;
1. FUEL WITH NO OIL(RAW GASOLINE) –
It will cause severe damage to the internal
engine parts very quickly.
2. GASOHOL – It can cause deterioration of
rubber and/or plastic parts and disruption
of engine lubrication.
3. OIL FOR 4-CYCLE ENGINE USE – It can
cause spark plug fouling, exhaust port
blocking, or piston ring sticking.
4. Mixed fuels which have been left
unused for a period of one month or
more may clog the carburetor and result
in the engine failing to operate properly.
5. In the case of storing the product for a
WARNING
long period of time, clean the fuel tank
after rendering it empty. Next, activate the
engine and empty the carburetor of the
composite fuel.
6. In the case of scrapping the used mixed
oil container, scrap it only at an authorized
repository site.
As lot details of quality assurance, read the
description in the section Limited Warranty
carefully. Moreover, normal wear and
change in product with no functional
influence are not covered by the warranty.
Also, be careful that, if the usage in the
instruction manual is not observed as to the
mixed gasoline, etc. described therein, it
may not be covered by the warranty.
NOTE

14 
■STARTING ENGINE
The cutting head will start rotating upon the
engine starts.
1. Rest the unit on a flat, firm place. Keep the
cutting head off the ground and clear of
surrounding objects as it will start rotating upon
starting of the engine.
2. Push the primer pump several times until
overflown fuel flows out in the return tube. (OP1)
3. Move the choke lever to the closed position.
(OP2)
(1) Choke lever (2) A: the closed position
(3) B: the open position
4. Set the ignition switch to the “start” position.
(OP3)
(1) Ignition switch (2) Stop
(3) Start
5. While holding the unit firmly, pull out the starter
rope quickly until engine fires. (OP4)
•Avoid pulling the rope to its end or returning it by
releasing the knob. Such actions can cause
starter failures.
6. Move the choke lever to the open position
(OP2). And pull out the starter rope quickly to
restart engine. (OP4)
7. Allow the engine to warm up for several minutes
before starting operation.
1. When restarting the engine immediately after
stopping it, leave the choke open (OP2) and
push the primer pump several times (OP4).
2. Overchoking can make the engine hard to start
due to excess fuel. When the engine failed to
start after several attempts, open the choke and
repeat pulling the rope, or remove the spark plug
and dry it.
NOTE
IMPORTANT
WARNING
8. Operation
OP1
(1)
A
B
(2)
(3)
OP2
OP3
OP4

8. Operation
■STOPPING ENGINE
1. Release the throttle lever and run the engine for
a half minute.
2. Shift the ignition switch to the STOP position.
•Except for an emergency, avoid stopping the
engine while pulling the throttle lever.
■ADJUSTING IDLING SPEED (OP5)
1. When the engine tends stop frequently at idling
mode, turn the adjusting screw clockwise.
2. When the cutting head keeps rotating after
releasing the trigger, turn the adjusting screw
counter-clockwise.
(1)Idle adjustment screw
•Warm up the engine before adjusting the idling
speed.
■LINE HEAD USAGE
1. Always wear eye protection such as safety
goggles. Never lean over the rotating cutting
head. Rocks or other debris could be thrown
into eyes and face and cause serious
personal injury.
2. Keep the debris guard attached in place at all
times when the unit is operated.
TRIMMING GRASS AND WEEDS
•Always remember that the TIP of the line does
cutting. You will achieve better results by not
crowding the line into the cutting area. Allow the
unit to trim at its own pace.
1. Hold the unit so the head is off the ground and is
tilted about 20 degrees toward the sweep
direction. (OP6)
2. You can avoid thrown debris by sweeping from
your right to the left.
WARNING
NOTE
NOTE
(1)
OP5
OP6
15 

16 
3. Use a slow, deliberate action to cut heavy
growth. The rate of cutting motion will depend on
the material being cut. Heavy growth will require
slower action than will light growth.
4. Never swing the unit so hard as you are in
danger of losing your balance or control of the
unit.
5. Try to control the cutting motion with the hip
rather than placing the full workload on the arm
and hands.
6. Take precautions to avoid wire, grass and dead,
dry, long-stem weeds from wrapping around the
head shaft. Such materials can stall the head
and cause the clutch to slip, resulting in damage
to the clutch system if repeated frequently.
ADJUSTING THE LINE LENGTH
•Your brushcutters is equipped with a semi- auto
type nylon line head that allows the operator to
advance the line without stopping the engine.
When the line becomes short, lightly tap the
head on the ground while running the engine at
full throttle.
•Each time the head is bumped, the line advance
about 1 inch(25.4 mm). For better effect, tap the
head on bear ground or hard soil. Avoid
bumping in thick, tall grass as the engine may
stall by overload.
8. Operation

9. Maintenance
Maintenance, replacement, or repair of the emission control device and systems may be
performed by any non-road engine repair establishment or individual.
•Always be sure to stop the engine before inspecting the brushcutter for problems or
performing maintenance.
•Never alter the brushcutter or take the engine apart.
•When replacing parts, always be sure to use only ZENOAH products or products which
have been certified by ZENOAH for use with the ZENOAH brushcutter.
•Things to check before using brushcutter.
■REFILLING TRIMMING LINE
WARNING
1 4 6
2 5 7
3
7.6m
(25')
3.8m
(12.5')
Ø2.4mm
0.095In
17 

18 
9. Maintenance
8 11 14
1
2
9
10 12
13
15
THIS
SIDE UP
THIS
SIDE UP
WIND
LINE

•Make sure that the engine has stopped and is
cool before performing any service to the
brushcutter. Contact with moving cutting
head or hot muffler may result in a personal
injury.
■AIR FILTER
•The air filter, if clogged, will reduce the engine
performance. Monthly check and clean the filter
element in warm, soapy water as required. Dry
completely before installing. If the element is
broken or shrunk, replace with a new one. (MA1)
(1)Air filter
■FUEL FILTER
•When the engine runs short of fuel supply, check
the fuel cap and the fuel filter for blockage.
(MA2)
(1)Fuel filter
■SPARK PLUG
•Starting failure and mis-firing are often caused
by a fouled spark plug. Periodically clean the
spark plug and check that the spark gap is in the
correct range. For a replacement plug, use the
correct type specified by ZENOAH(See
SPECIFICATIONS on the page 3). (MA3)
•When you take off the spark plug, twist (1) and
pull off the cap (2). (MA4)
•REPLACEMENT PLUG IS A CHAMPION
RCJ6Y OR THE EQUIVALENT, SUCH AS
BOSCH WSR8E OR NGK BPMR7A.
•Note that using any spark plugs other than those
designated may result in the engine failing to
operate properly or in the engine becoming
overheated and damaged.
•To install the spark plug, first turn the plug until it
is finger tight, then tighten it a quarter turn more
with a socket wrench. 87~104 in-lbs
TIGHTENING TORQUE: (9.8~11.8 N.m.)
IMPORTANT
WARNING
9. Maintenance
MA3
MA2
(1)
MA1
MA4
19 

20 
■MUFFLER
•Inspect periodically, the muffler for loose
fasteners, any damage or corrosion. If any
sign of exhaust leakage is found, do not use
the brushcutter and have it repaired
immediately.
•Note that failing to do so may result in the
engine catching on fire.
■SPARK ARRESTER
•The muffler is equipped with a spark arrester to
prevent red hot carbon from flying out of the
exhaust outlet. Periodically inspect and clean as
necessary with a wire brush. In the State of
California it is required by law (Section 4442 of
the California Public Resources Code) to equip a
spark arrester when a gas powered tool is used
in any forest covered, brush covered, or grass
covered unimproved land. (MA5)
(1)Spark arrester
■INTAKE AIR COOLING VENT
•Never touch the cylinder, muffler, or spark
plugs with your bare hands immediately after
stopping the engine. The engine can
become very hot when in operation, and
doing so could result in severe burns.
•When checking the brushcutter to make sure
that it is okay before using it, check the area
around the muffler and remove any wood
chips or leaves which have attached
themselves to the brushcutter. Note that
failing to do so could cause the muffler to
become overheated, and that this in turn
could cause the brushcutter to catch on fire.
Always make sure that the muffler is clean
and free of wood chips, leaves, and other
waste before use.
•Check the intake air cooling vent and the area
around the cylinder cooling fins after every 25
WARNING
WARNING
9. Maintenance
(1)
MA5