Hyundai HDBT421T Gasoline Brush Cutter & Grass Trimmer

Original Instructions

Content

1. Safety Warnings

Proper safety precautions must be observed. Like all power equipment, this unit must be handled carefully. DO NOT EXPOSE YOURSELF OR OTHERS TO DANGER.

Follow these general rules. Do not permit others to use this machine unless they are thoroughly responsible and have read and understand the machine manual and are trained in its operation.

Explanation of Symbols

Symbol Description
⚠️ This graphic accompanied by the words WARNING and DANGER calls attention to an act of a condition which can lead to SERIOUS INJURY.
? READ & UNDERSTAND Operator's Manual and Safety Manual
⛑️?⛑️ ALWAYS WEAR EYE PROTECTION, EAR PROTECTION AND HEAD PROTECTION.
?? WEAR FOOT PROTECTION, WEAR GLOVES
⚠️ BEWARE OF FALLING OBJECTS
⚠️ BEWARE OF FOOT INJURY BY CUTTING ATTACHMENT
⚠️ PAY ATTENTION THAT BYSTANDERS ARE NOT INJURED THROUGH FOREIGN OBJECTS THROWN FROM THE MACHINE.
⚠️ BEWARE OF THROWN OBJECTS HIT BY CUTTING ATTACHMENTS. NEVER USE WITHOUT PROPERLY MOUNTED BLADE GUARD. BEWARE OF BLADE THRUST.
?15m KEEP BYSTANDERS AT LEAST 15 M AWAY.
?? DO NOT USE SAW BLADE.
⚠️ RISK OF HOT SURFACE
? 120 dB(A) GUARANTEE SOUND POWER LEVEL

2. Your Product

a. Description

The Hyundai HDBT421T is a Gasoline Brush Cutter & Grass Trimmer designed for various cutting applications.

Components:

b. Technical Data

Specification Model: HDBT421T
Remote type Centrifugal Clutch; Hard transmission
Maximum speed of cutter head (r/min) 8,000
Idle speed of engine (r/min) 3,000 ±300
Centrifugal speed (r/min) 3,800
Measured vibration emission value (m/s²) (According to ISO 22867) Brush cutter: Left handle: 7.126, Right handle: 7.867
Grass trimmer: Left handle: 8.918, Right handle: 10.17
K=1.5
Measured sound pressure level LpA dB(A) (According to ISO 22868) Brush cutter: 97 dB (A), Grass trimmer: 98 dB (A)
K=3 dB (A)
Measured sound power level LwA dB(A) (According to ISO 22868) Brush cutter: 107 dB (A), Grass trimmer: 108 dB (A)
K=3 dB (A)
Guaranteed sound power level 120 dB (A)
Line Max. Cutting Path /Diameter of line 44 cm (2.5mm, 7,500 min⁻¹)
Metal blade (Type/Diameter) 3-tooth, Ø230xØ25.4x1.4mm, 8,000 min⁻¹
Rotation direction of cutting device Counter-Clockwise (seen from the top)
Type of aluminum pole 1 piece
Weight when dry (kg) 7.3
Engine Name SPK1E40F(1)
Engine Type Air-cooled; 2 cycle; vertical Piston valve; gasoline engine
Displacement (cm³) 43
Maximum output (kW) (in accordance with ISO 8893) 1.23
Maximum speed of engine (/min) 10,000
Specific fuel consumption at max. engine performance (g/kWh) ≤620
Carburetor Diaphragm-type
Ignition Non-contact electronic ignition
Method of starting Recoil type
Fuel used Gasoline mixed with lubricating oil (ratio of 40:1)
Fuel tank capacity (cm³) 1200

3. Assembly

Installing Handle

Install the handle in the bracket. Position the handle in a comfortable operating position and tighten the four bolts.

Diagram showing handle installation with screws and bracket.

Installing the Guard of Protection

Install the guard of protection on the housing. Screw it with the two provided screws.

Installing Nylon Line Cutter Head (for Grass Trimming)

Align the hole of the upper plate with the hole in the shaft and insert a locking tool (such as a wrench). Remove the locking nut and the lower plate. Install the line cutter head by turning it counter-clockwise until it is tight. Remove the locking tool.

To remove the cutting head, insert a locking tool into the hole of the shaft, then unscrew the cutting head. This must be done when the tool is off and cooled.

Images showing the process of installing the nylon line cutter head.

Installing the Metal Blade (for Brushcutting)

When installing and removing the blade, pay attention to its sharp edges. Wear protective gloves.

Align the hole of the upper plate with the hole in the shaft and insert a locking tool (such as a wrench). Remove the locking nut and the lower plate. Install the blade on the upper plate. Install the lower plate. Then, screw the locking nut to secure the installation.

Images showing the process of installing the metal blade, with a note about maximum RPM.

Do the inverse steps to remove the blade.

Installing the Shoulder Strap

Hang the harness in its dedicated location on the tube. Adjust the size of the harness properly to have a correct working position.

Image showing the shoulder strap attachment.

Please do not use both functions at the same time. Before using the tool, check that the tubes, cutting accessories, and the harness are properly installed.

4. Operation

Rules for Safe Operation

WARNING! DANGER

All models of trimmers and brush cutters can throw small stones, metal, or small objects, as well as the material being cut. Read these “Rules for Safe Operation” with care.

Follow the instructions in your operator's manual. Read the operator's manual carefully. Be thoroughly familiar with the controls and proper use of the unit. Know how to stop the unit and shut off the engine. Know how to unhook a harnessed unit quickly.

Never allow anyone to use the unit without proper instruction. Be sure the operator wears the foot, leg, eye, face, and hearing protection from thrown objects. Keep the area clear of bystanders, children, and pets. Never allow children to operate or play with the unit.

Do not allow anyone to enter the operating DANGER ZONE with you. The danger zone is an area 15 meters in radius (about 50 feet).

Insist that persons in the RISK ZONE beyond the danger zone wear eye protection from thrown objects. If the unit must be used where there are unprotected people, operate at a low throttle speed to reduce the risk of thrown objects.

Move the stop switch to the "o" position when the engine idles; ensure it is reliable before cutting. Only continue to operate the unit when the stop switch is in good condition. Routinely check that the cutting attachment stops turning when the engine idles.

WARNING! DANGER

In addition to head, eye, face, and ear protectors, shoes to protect your feet improve your footing on slippery surfaces. Do not wear ties, jewelry, or loose, dangling clothing which could be caught in the unit.

Do not wear open-toed footwear, or go bare-foot or bare-legged. In certain situations, you must wear total face and head protection.

Diagram illustrating the 15-meter danger zone around the operator.

DANGER ZONE

NO PERSON EXCEPT OPERATOR ALLOWED WITHIN 15 METERS RADIUS DANGER ZONE. EYE, EAR, FACE, FOOT, LEG AND BODY PROTECTION MUST BE WORN BY OPERATOR. PERSONS IN ZONE OR RISK BEYOND DANGER ZONE SHOULD WEAR EYE PROTECTION AGAINST THROWN OBJECTS. RISK DIMINISHES WITH DISTANCE FROM DANGER ZONE.

Cutting with a Nylon Head

WARNING! DANGER

The proper debris shield must be in place on the unit when nylon cutting line is used. The cutting line can flap around if too much line is exposed. Always use the plastic debris shield with the cut-off knife when using nylon cutting heads.

For nearly all cutting, it is good to tilt the line head so that contact is made on the part of the line circle where the line is moving AWAY from you and the debris shield. This results in the debris being thrown AWAY from you.

WARNING! DANGER

Tilting the head to the wrong side will shoot the debris TOWARDS you. If the line head is held flat to the ground so that cutting occurs on the whole line circle, debris will be THROWN at you, drag will slow the engine down, and you will use up a lot of line.

WARNING! DANGER

Use only quality nylon monofilament line of the diameter 2.5mm. Never use wire or wire-reinforced line in place of nylon trimmer line. Load your nylon line cutting head only with nylon trimmer line of the proper diameter.

WARNING! DANGER

Use extreme caution when operating over bare spots and gravel, because the line can throw small rock particles at high speeds. Debris shields on the unit cannot stop objects which bounce or ricochet off hard surfaces.

Trimming

This is feeding the trimmer carefully into the material you wish to cut. Tilt the head slowly to direct debris away from you. If cutting up to a barrier such as a fence, wall, or tree, approach from an angle where any debris ricocheting off the barrier will fly away from you. Move the line head slowly until the grass is cut right up to the barrier, but do not jam (overfeed) the line into the barrier. If trimming up to a wire mesh or chain-linked fence, be careful to feed only up to the wire. If you go too far, the line will snap off around the wire. Trimming can be done to cut through weed stems one at a time. Place the trimmer line head near the bottom of the weed—never high up, which could cause the weed to chatter and catch the line. Rather than cut the weed right through, just use the very end of the line to wear through the stem slowly.

WARNING! DANGER

Do not use a steel blade for edging or scalping.

Scalping and Edging

Both of these are done with the line head tilted at a steep angle. Scalping is removing top growth, leaving the earth bare. Edging is trimming the grass back where it has spread over a sidewalk or driveway. During both edging and scalping, hold the unit at a steep angle and in a position where the debris, and any dislodging dirt and stones, will not come back towards you even if they ricochet off the hard surface. Although the picture shows how to edge and scalp, every operator must find for himself the angles which suit his body size and cutting situation.

WARNING! DANGER

Do not trim in any area where there are strands of fencing wire. Wear protective safety gear. Do not cut where you cannot see what the cutting device is cutting.

Cutting with a Blade

The machine is provided with a 3-tooth metal blade for cutting brush and weeds up to 3/4" in diameter.

Use of a saw blade with this machine is prohibited.

WARNING! DANGER

DO NOT USE A BRUSH CUTTER FOR CUTTING TREES.

WARNING! DANGER

Do not cut with a dull, cracked, or damaged metal blade. Before cutting growth, inspect for obstructions such as boulders, metal stakes, or strands of wire from broken fences. If an obstruction cannot be removed, mark its location so that you can avoid it with the blade. Rocks and metal will dull or damage a blade. Wire can catch on the blade head and flap around or be thrown into the air.

WARNING! DANGER

Use the shoulder harness at all times. Adjust both harness and harness clamp on the unit so that the unit hangs a few inches above ground level. The cutting head and the debris shield should be level in all directions. Harness the unit on the right side of your body.

Sc ything Weeds

This is cutting by swinging the blade in a level arc. It can quickly clear areas of field grass and weeds. Scything should not be used to cut large, tough weeds or woody growths.

NOTE: Do not use a brush blade to cut trees which exceed a diameter of 1/2 to 3/4 inches.

Scything can be done in both directions, or just in one way which results in the debris being thrown away from you. That is using the side of the blade that is rotating away from you. Tilt down the blade slightly on this same side. You will be hit by some debris if you scythe in both directions.

Cut only with the side of the blade that the debris is moving away from you.

If kickback occurs, the blade may be dull, or the material so thick and hard that you should use other tool instead of this machine.

Do not force the blade to cut. Do not change the angle of cut after into the wood. Avoid using any pressure or leverage which could cause the blade to bind or crack.

Fuel & Oil Mixture

Never fill the fuel tank to the very top. Never add fuel to the tank in a closed, non-ventilated area. Do not add fuel to this unit close to an open fire or sparks. Be sure to wipe off spilled fuel before attempting to start the engine. Do not attempt to refuel a hot engine.

Fuel used for this model is a mixture of unleaded gasoline and approved engine lubricant. When mixing gasoline with two-cycle engine oil, use only gasoline which contains NO ETHANOL or METHANOL (Types of Alcohol). Use Branded 89 octane or higher Unleaded gasoline known to be of good quality. This will help to avoid possible damage to engine fuel lines and other engine parts.

MIXTURE RATIO IS 40:1

GASOLINE-40PART, OIL-1 PART

The engine uses two-stroke fuel, a mixture of gasoline and 2-stroke lubricant 40:1.

Fuel mixture at the rate other than 40:1 may cause damage to the engine. Ensure mixture ratio is correct.

IMPORTANT: Two-stroke fuel may separate. Shake fuel container thoroughly before each use. Stored fuel ages. Do not mix more fuel than you expect to use within a month.

GASOLINE: Use branded 89 octane or higher unleaded gasoline known to be of good quality.

STORING FUEL: Store fuel only in a clean, safe, approved container. Check and follow local ordinances on type and location of storage container.

FUEL AND OIL MIXTURE: Inspect fuel tank, making sure that it is clean and fill with fresh fuel. Use a mixture of 40:1.

Preparing for Operations

WHEN MIXING GASOLINE WITH TWO CYCLE ENGINE OIL, USE ONLY GASOLINE WHICH CONTAINS NO ETHANOL OR METHANOL (TYPES OF ALCOHOL). THIS WILL HELP TO AVOID POSSIBLE DAMAGE TO ENGINE FUEL LINES AND OTHER ENGINE PARTS. DO NOT MIX GASOLINE AND OIL DIRECTLY IN THE ENGINE FUEL TANK.

IMPORTANT: Failure to follow proper fuel mix instructions may cause damage to the engine.

  1. When preparing fuel mixture, mix only the amount needed for the job you are to do. Do not use fuel that has been stored longer than two months. Fuel mixture stored longer than this will cause hard starting and poor performance. If fuel mix has been stored longer than this time, it should be removed and filled with fresh mixture.

WARNING! DANGER

  1. Never fill the fuel tank to the very top.
  2. Never add fuel to the tank in a closed non-ventilated area.
  3. Do not add fuel to this unit close to an open fire or sparks.
  4. Be sure to wipe off spilled fuel before attempting to start engine.
  5. Do not attempt to refuel a hot engine.

Check Points Before Operation

  1. Check for loose bolts, nuts, and fittings.
  2. Check the air cleaner for dirt. Clean the air filter of all dirt, etc., before operation.
  3. Check to be sure that the protector is securely in place.
  4. Check to be sure that it is not leaking.
  5. Check to be sure the blade is not running in idling speed.

WARNING! DANGER

The engine exhaust from this product contains chemicals known to cause cancer, birth defects, or other reproductive harm.

Operations

Engine Starting and Stopping Procedures

1. First Use and Cold Engine Start

  1. Set the On / Off switch to the On position (I). (See Pic. A)
  2. Put the choke in the OFF position. (See Pic. B)
  3. Press the priming pump, located under the air filter cover, about 7 to 10 times until the fuel enters the carburetor. (See Pic. C)
  4. Pull the starter gently until you feel a resistance, then pull with a sharp blow. Be careful to accompany the handle to avoid a sudden return of it on the engine of the machine. (See Pic. D)
  5. After the machine has started, return the choke to the ON position. (See Pic. E)
  6. Allow the machine to warm up for 2-3 minutes.

2. Warm Engine Start

  1. To restart the machine when the engine is warm, put the choke in the ON position.
  2. Pull the starter gently until you feel a resistance, then pull with a sharp jerk.
  3. Let the engine run until it reaches a steady state.

3. Stopping

WARNING! The cutting device may continue to run for a few seconds after stopping the machine.

  1. Release the throttle trigger and let the engine idle.
  2. Turn the ON/OFF switch to the off position (O).

If you experience unusual and excessive vibrations, stop the machine immediately. Perform the checks to determine the cause.

5. Maintenance & Care

Air Filter

Adjusting Carburetor

NOTE: Do not adjust carburetor unless necessary. If you have trouble with the carburetor, see your dealer. Improper adjustment may cause engine damage and void warranty.

Fuel Filter

Check Spark Plug

6. Troubleshooting

Clean or replace the plug if fouled with heavy oily deposits. Replace the plug if the center electrode is worn rounded at the end.

WARNING: Always cover the metal blade with the transportation guard while transportation and storage.

Transport, Handling

Extended Storage

Failures such as difficulty in starting the engine, irregularity in functions, and abnormality in performance can normally be prevented if careful attention is paid to all operating instructions and maintenance procedures.

Should the engine not function properly, check the following:

Failure to Start

When there is serious trouble with the unit, do not try to repair it yourself but have your distributor or dealer do it for you.

Troubleshooting Guide: Failure to Start

Symptom Probable Cause Remedy
Cylinder
normal
Fuel system abnormality
Fuel filter obstruct
Add fuel in tank
Clean fuel filter
Fuel is too dirty
There is water in fuel
There is too much mixture ratio is improper
Replace fuel
Replace fuel
Tear down spark plug and dry it
Mixture peroration
Spark plug fouled with oily deposits
Spark plug insulation damage
Spark gap is too large or small
Clean the oil deposits
Replace spark plug
Adjust spark gap 0.6-0.7mm
Compress
normal
High voltage wire breach or break off
Coil looseness
Replace or tighten
Tighten
Piston ring attrition
Piston ring is broken
Piston ring cementation
Spark plug looseness
Conjoint surface of the cylinder and crank cast leak
Replace a new
Replace
Eliminate
Tighten
Eliminate
Fuel system
normal
Ignition
shortage
High voltage wire and spark plug contact badness
Stop switch failure or short circuit
Tighten the spark plug cap
Repair or replace

Troubleshooting Guide: Low Output

Muffler fouled with oily deposits Piston, piston ring, cylinder attrition,
Conjoint surface of the cylinder and crank cast leak
The seal is bad
Symptom Probable Cause Remedy
Flameout when speedup Fuel filter obstruct, fall short of fuel Clean fuel filter, clean fuel road, adjust carburetor
The smoke is thin, carburetor spout backward Clean the oily deposits
Compress press is shortage Replace piston, piston ring
Repair
Replace seal
Engine leak Engine overheats Avoid use it for long time, high speed and heavy load
The end of two crank shaft leak Burning room fouled with oily deposits Clean the oily deposits

Troubleshooting Guide: Engine Running Unstable

Piston, piston ring, cylinder attrition,
Piston pin, piston attrition
Bearing of crank shaft attrition
Symptom Probable Cause Remedy
There are metal knock sound Replace piston, piston ring
Replace piston pin, piston
Replace bearing
There are metal knock sound Engine overheats
Burning room fouled with oily deposits
Avoid use it for long time, high speed and heavy load clean the oily deposits
Engine ignition break off Gasoline branded is unfit
There is water in fuel
Spark gap is wrong
Coil gap is wrong
Replace required branded octane
Instead fuel
Adjust spark gap 0.6-0.7mm
Adjust coil gap 0.3-0.4mm

Troubleshooting Guide: The Engine Suddenly Stopped

Probable Cause Remedy
Fuel is use up Add fuel
Spark plug fouled with oily deposits and short circuit Clean the oily deposits
High voltage wire fall off Connect

7. Declaration of Conformity

HYUNDAI POWER PRODUCTS

CE

Genpower Ltd

Isaac Way London Road Pembroke Dock Pembrokeshire SA72 4RW United Kingdom

Declares that the machines:

Gasoline Brush Cutter & Grass Trimmer

Model: HDBT421T

Serial No.: 20250801551-20250801800

Have been designed in compliance with the following standards:

And in accordance with the following directives:

Measured sound power level LwA dB(A) (According to ISO 22868): Brush cutter: 107 dB (A), Grass trimmer: 108 dB (A), K=3 dB (A)

Guaranteed sound power level (According to ISO 2000/14/EC): 120 dB (A)

Responsible of the Technical file: Mr. Mark Z

Done at Pembrokeshire: 01/07/2025

Signature of Mr. Mark Z

Name of QC manager: Roland Llewellin

8. Warranty

The manufacturer guarantees the product against defects in material and workmanship for a period of 2 years from the date of the original purchase. The warranty only applies if the product is for household use. The warranty does not cover breakdowns due to normal wear and tear.

The manufacturer agrees to replace parts identified as defective by the designated distributor. The manufacturer does not accept responsibility for the replacement of the machine, in whole or in part, and/or ensuing damage.

The warranty does not cover breakdowns due to:

The warranty does not extend to:

Due to Hyundai's policy of continuous product improvement, specifications may be altered or changed without notice. Consequently, the product may differ from the information contained herein, but a modification will be undertaken without notice if it is recognized as an improvement of the preceding characteristic.

READ THE MANUAL CAREFULLY BEFORE USING THE MACHINE.

When ordering spare parts, please indicate the part number or code, which can be found in the spare parts list in this manual. Keep the purchase receipt; without it, the warranty is invalid. To help you with your product, contact Hyundai by phone or via their website:

+33 (0)9.70.75.30.30

https://services.swap-europe.com/contact

To create a "ticket" via the web platform:

Logo of SWAP-Europe.

9. Product Failure

What to do if my machine breaks down?

If you bought your product in a store:

If you bought your product on a website:

For machines with engine failure from manufacturers BRIGGS & STRATTON, HONDA, and RATO, please refer to the following instructions.

Repairs will be done by approved engine manufacturers of these manufacturers; see their sites:

Please keep your original packaging to allow for after-sales service returns or pack your machine with a similar cardboard box of the same dimensions.

For any question concerning after-sales service, you can make a request on our website https://services.swap-europe.com.

Our hotline remains available at +33 (9) 70 75 30 30.

SWAP logo.

10. Warranty Exclusions

THE WARRANTY DOES NOT COVER:

* In accordance with transport legislation, damage related to transport must be declared to carriers within 48 hours maximum after observation by registered letter with acknowledgement of receipt.

This document is a supplement to your notice, a non-exhaustive list.

Attention: All orders must be checked in the presence of the delivery person. In case of refusal by the delivery person, you must simply refuse the delivery and notify your refusal.

Reminder: The reserves do not exclude the notification by registered letter with acknowledgement within 72 hours.

Information:

Thermal devices must be wintered each season (service available on the SWAP-Europe site). Batteries must be charged before being stored.

Contact Information

For inquiries, please contact:

Genpower Ltd

Isaac Way London Road Pembroke Dock Pembrokeshire SA72 4RW United Kingdom

T: +44 (0)1646 687880 | F: +44 (0)1646 686198

www.hyundaipowerequipment.co.uk

Fabriqué en République Populaire de Chine(PRC)

Importer by Genpower Ltd

Licensed by Hyundai Corporation Holdings, Korea

Models: EN, 20250701, HDBT421T Gasoline Brush Cutter and Grasstrimmer, Gasoline Brush Cutter and Grasstrimmer, Brush Cutter and Grasstrimmer, Cutter and Grasstrimmer, Grasstrimmer

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HDBT421T EN manual 20250701

References

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