The engine exhaust fromthis product contains chemicals knownto the State of California to cause cancer, birth defects, or other reproductive harm. Keep this owner’s manual handy, so you can refer to it at any time. This owner’smanual is considered a if resold. permanent part of the trimmer/brush cutterand should remain with the trimmer/brush cutter The information and specifications included in this publication were in effect at the time of approval for printing. Honda Motor Co., Ltd.
INTRODUCTION Congratulations on your selection of a Honda trimmer/brush cutter. We are certain you will be pleased with your purchase of one of the finest trimmers/brush cutters on the market. We want to help you get the best results from your newtrimmer/brush cutter and to operate it safely. This manual contains the information on how to do that; please read it carefully. As you read this manual,you will find information precededbyasymbol.
INTRODUCTION A FEW WORDS ABOUT SAFETY Your safety and the safety of others are very important. Andusing this trimmer/brush cutter safely is an important responsibility. To help you make informed decisions about safety, we have provided operating procedures and other information on labels and in this manual. This information alerts you to potential hazards that could hurt you or others.
ection CONTENTS TRIMMER SAFETY ............................................ 4 IMPORTANT SAFETY INFORMATION .......................... 4 ATTACHMENTS & MODIFICATIONS .............................. 5 Attachments............................................................................ 5 Modifications ........................................................................... ...................5 IMPORTANT MESSAGE EMPLOYERS TO SAFETY LABEL LOCATIONS.......................................... 6 ...
TRIMMER SAFETY IMPORTANT SAFETY INFORMATION Honda UMK422 and UMK431trimmerdbrush cutters are designed to cut grass, weeds, brush, and/or wood if equipped with an appropriate cutting attachment. Other uses can resultin injury to the operator or damage to the trimmer and other property. Turn the EngineOff When Not Trimming 0 Keep People Away From Your Working Area These Honda trimmers are intended for use by gardening professionals. Never allow childrento operate the trimmer.
TRIMMER SAFETY ATTACHMENTS & MODIFICATIONS IMPORTANT MESSAGE TO EMPLOYERS Modifying your trimmer/brush cutter, or installing non-Honda attachments, can make your trimmer unsafe. Before youmake any modifications or install any attachments, be sure toread the following information. As an employer, you have special responsibilities to the people who work for you.
TRIMMER SAFETY SAFETY LABEL LOCATIONS The labels shown here contain important safety information. Please read them carefully. These labels are considered permanent parts of your trimmer/brush cutter. If a label comes off or becomes hard to read, contact an authorized Honda servicing dealer for a replacement. 1 I II A W A R N I N G I OWNERS MANUAL. q I Failure to do so can result in serious injury to the oDerator and bystanders.
RECOMMENDED CUTTING ATTACHMENTS CUTTING-LINE HEADSAND SHIELD A cutting-line head containing nylon monofilament line, and a debris shield with cutoff knife is standard equipment. The shield’s cutoff knife automatically removes any excess line that is released from the cutting head. CUTTING-LINE HEAD \ NYLON MONOFILAMENT LINE I Honda UMK431 UNBAtrimmers are supplied with two different debris shields. Use the debris shield with the cutoff knife when the cutting-line head is installed.
RECOMMENDED CUTTING ATTACHMENTS ELDANDBLADES CUlTlNG LINE DEBRIS SHIELD SHIELD DEBRIS BLADE p A variety of blades are available from your Honda trimmer servicing dealer. Always use a debris SHIELD FOR GRASSNEED BLADE, shield designed for use with a blade when WEED/BRUSH BLADE attaching a blade to your trimmer. This type of debris shield does not havea cutoff knife. DEBRIS SHIELD FOR BRUSHNOOD BLADE Honda UMK431UNBA trimmers are supplied with a blade cover surrounding the edge of the blade.
RECOMMENDED CUTTING ATTACHMENTS Brush/Wood Blade Cover Installation and Removal DEBRIS SHIELD BLADE \ \ 1. Place the blade cover on the blade halfway, ENDA starting with endA. To prevent the posts on end A from interfering with the debris shield, remove end A from the blade andplace it beside the blade as shown. 2. Turn the blade slowlyuntil end A is clear of the debris shield. END 6' 3. Replace end A on the blade. 4.
CONTROLS & EQUIPMENT COMPONENT & CONTROL LOCATIONS CHOKELEVER SPARKPLUGCAP f i FUEL RETURN TUBE [Jear) \ FUEL SUPPLY TUBE (black) FUEL TANK CUTTING-LINE HEAD I GEAR CASE STARTER GRIP LOOP HANDLE ARNESS HANGER THROlTLE SET BUlTON DEBRIS SHIELD WITH ORPRESENCELEVER CUTOFF KNIFE A DRIVE SHAFT HOUSING IGNITION SWITCH GEAR CASE UMK431 UNBA (supplied withtwo cutting attachments and debris shields) BLADE, THROlTLE SET BUlTON DEBRIS SHIELD FOR BRUSHMOOD BLADE -HARNESS I e DRIVE SHAFT HOUSING CUTTI
I CONTROLS & EQUIPMENT CONTROLS CHOKE LEVER Choke Lever The choke lever opens andcloses the choke valve. 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. Ignition Switch Loop handle: U-type The ignition switch controls the ignition system.handle: IGNITION SWITCH BUTTON The ignition switch button must be in the ON ( I ) position for the engine to start and run.
CONTROLS & EQUIPMENT Throttle Set Button THROlTLE SET BUlTON The throttle set buttonis usedto hold the throttle trigger at the fast idle position for starting.
CONTROLS & EQUIPMENT EQUIPMENT Honda UMK422 and UMK431 trimmerdbrush cutters are suppliedwith a shoulder harness and safety glasses. Refer topage 14for a description of other equipmentand protective clothing youwill need. FULL SHOULDER HARNESS n Shoulder Harness A full shoulder harness must be worn by the operator of these Honda trimmers/brush cutters when equipped with a blade and debris shield.
ARE YOU READY TO OPERATE THE TRIMMER? Your safety is your responsibility. A little time spent in preparation will significantly reduce your risk of injury. Knowledge Read and understand this manual. Know whatthe controls do and how to operate them. Familiarize yourself with the trimmer and its operation before you begin to use it. Know what to do in case of emergencies. Physical and Mental Readiness You must be alert and in good physical condition to operate the trimmer.
BEFORE OPERATION IS YOUR TRIMMER READY TOGO? For your safety,and to maximize the service life of your equipment, itis very important to take a few moments before you operate the trimmer to check its condition. Be sureto take care of any problem you find, or have your servicing dealer correct it, before you operate the trimmer. Cutting Attachment Inspection Look for signsof damage to the cutting attachment (see pages 33 and 39).
BEFORE OPERATION ARE YOUR SHOULDER HARNESS AND TRIMMER CORRECTLY ADJUSTED? Adjusting Harness Shoulder Balancing the the Trimmer on the Adjust the harness so the quick-release latch is your at right hip, shown. as Hang Harness the trimmer on the harness hook, and see how it balances.
OPERATION SAFE OPERATING PRECAUTIONS Before operating the trimmer forthe first time, please reviewthe IMPORTANT SAFETY INFORMATlON on page 4 and the chapter titled BEFORE OPERATION. Even if you have operated other trimmers, take time to become familiar with the operation of this trimmer’s controls and handling. For your safety, avoid starting or operating the engine in an enclosed area, such as agarage.
OPERATION I 5. Set the trimmer on the ground, resting on the debris shield and the fuel tank guard. Do not allow the cutting line or blade to contact any obstruction. Always rest the trimmer on the ground for starting, rather than holding it in the operating position. That prevents the end of the trimmer from swinging into something as you start the engine. 6. With your left hand, hold the drive shaft housing just ahead of the engine.
OPERATION STOPPING THE ENGINE 1. Release the throttle lever. IGNITION .SWITCH BUlTON OFF (0) 2. Move the ignition switch button to the OFF (0) position. Wait for the cutting line head or blade to stop before allowing the end of the trimmer to contact anything. The blade will continue to spin briefly after the engine has stopped or the throttle trigger is released. A coasting blade can cause injury. LATCH TAB Maintain proper controlof the trimmer until the blade has completely stopped rotating.
OPERATION Throttle Operation Pull the throttle trigger toward the grip to increase engine speed and start cutting attachment rotation. THROlTLE The trimmer has the greatest cutting force at maximum engine speed. Release the throttle trigger to reduce engine speed. At idle, the cutting attachment should coast to a stop. attachment stops) Using a Nylon Cutting-Line Head As the ends of the line wear away, more line must be released from the cutting-line head.
OPERATION Using Blades Thrown Debris Refer to the chart on page 9 for appropriate blade applications. The trimmer will throw debris in the direction of blade movement at the point of contact. If using a blade on a Honda trimmer equipped with a loop handle, also install the Honda conversion kit that includes a full shoulder harness, a barrier bar, and a debris shield for blades. Follow the installation instructions and safety information that come with the kit.
OPERATION Blade Thrust (Kickback) n Blade thrust (kickback) is the sudden, forceful, and uncontrolled movement of a blade-equipped trimmer that may occur if the blade binds in the cut or strikes a solid object. Blade thrust (kickback) throws the trimmer in the direction opposite blade rotation at the point of contact, and the jolt received by the operator can result in further loss of control.
OPERATION Trimming and Edging Use nylon line for cutting against a hard surface. Work from an angle where debris that strikes the hard surface will ricochet away from you. Avoid contact with wires, wire fences,metal rods, etc. Overlapping a wire will cause the nylon line to wrap around the wire and break off. Brush Clearing Clearing brush with a brush blade may require both scything and sawing. Scything with the right side of the blade will direct thrown debris away from you.
SERVICING YOUR HONDATRIMMER THE IMPORTANCE OF MAINTENANCE MAINTENANCE SAFETY Good maintenance is essential for safe, economical, and trouble-free operation. It will also help reduce air pollution. Some of the most important safety precautions follow. However, we cannot warn youof every conceivable hazard that can arise in performing maintenance. Only youcan decide whether or not you should performa given task.
SERVICING YOUR HONDA TRIMMER MAINTENANCE SCHEDULE I Every 2 REGULAR SERVICE PERIOD (3) Before each Perform at every indicated month or operating or ITEM whichever interval, first. comes hour Engine oil I I I 10 Hrs.
SERVICING YOUR HONDA TRIMMER ENGINE FILLER OPENING Engine Oil Level Check Check the engine oil level before each use, or every 10 hours if operated continuously. Rest the trimmer on a level surface, with the engine stopped and in an upright position. 1. Remove the filler cap/dipstick and wipe it clean. . Insert and remove the dipstick without screwing it into the filler opening. Check the oil level shown on the dipstick.
SERVICING YOUR HONDA TRIMMER Engine Oil Recommendations Oil is a major factoraffecting performance and service life. Use4-stroke automotive detergent oil. SAE 1OW-30 is recommended forall temperatures withinthe recommended operating range for these trimmers. The recommended operating range extends from 23°F (-5°C) to 104°F (40°C). The SAE oil viscosity and serviceclassification are in the API label on the oil container. Honda recommends that you use API SERVICE categorySJ oil.
SERVICING YOUR HONDATRIMMER Spark Plug Service Recommended Sparkplugs: CRSHSB (NGK) U16FSR-UB (DENSO) SPARK PLUG I I NOTICE I Incorrect spark plugs can cause engine damage. 1. Disconnect the spark plug cap, and remove any dirt from around the spark plug area. 2. Remove the spark plug with a 5/8-inch spark plug wrench. 3. Inspect the spark plug. Replace it if the electrodes are worn, or if the insulator is cracked or chipped. Clean the spark plug with a wire brush if you are going to reuse it.
SERVICING YOUR HONDATRIMMER Spark Arrester Service 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 very hot. Allowthe muffler to cool before servicing the spark arrester. 1. Remove the four 5 x 18 mm bolts from the recoil starter, and remove the recoil starter. 2. Disconnect the spark plug cap from the spark plug. Pull the spark plug wire and the ignition switch wire outof the retainers in the top cover.
SERVICING YOUR HONDA TRIMMER ~ Cooling Fin Inspection Inspect the engine cooling fins, and clean out dirt and debris if they are clogged. ENGINE COOLING FINS If it is necessary to remove the top cover for better access to the cooling fins, follow disassembly steps 1 through 3 on page 29. Throttle Cable Inspection Verify that the throttle trigger operates smoothly, and the throttle cable is undamaged.
SERVICING YOUR HONDA TRIMMER FUEL SYSTEM Refueling Fuel tank capacities UMK422: 0.48 US qt115.2fl. oz (0.45 2) UMK431: 0.69 US qt122.0fl. oz (0.65 2) FUEL TANK CAP Check the fuel level by looking through the translucent fuel tank. 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 first. To refuel, rest the trimmer on theground with the fuel tank cap facing up, as shown.
SERVICING YOUR HONDATRIMMER Fuel Filter and Fuel Tank Cleaning n 1. Remove the fuel tank cap, and emptythe fuel tank into an approvedgasoline container. Use a funnel to avoid spilling gasoline. 2. Pull the fuel filter out through the fuel filler neck by hooking the black fuel supply tube with a piece of wire, such asa partly straightened paper clip. 3. Inspect the fuel filter. If the fuel filter is dirty, wash it with nonflammable solvent. Becareful to avoid damaging the filter.
SERVICING YOUR HONDA TRIMMER CUTTING ATTACHMENTS Installing Replacement Nylon Line There are severalcutting attachments for your trimmer. Use the following section to inspect, remove, service and install a standard (factoryinstalled) cutting attachment. First, determine which cutting-line head style is on your trimmer. Amanual-feed trimmer head has a three-sided knob on the bottom of the head, while the semiautomatic head has a spring-loaded round button on the bottom of the head.
SERVICING YOUR HONDA TRIMMER DRUM Manual-Feed Cutting-Line Head 1. Clean any mud, dirt,debris, etc. from the area around the trimmer head; otherwise, it will make it more difficult to service. 2. Remove the three-sided knob; it has a lefthand thread, so turn it clockwise to remove. Remove the tension spring. 3. Remove the trimmer head from the drive bolt. / 4. Clean any debris, dirt, or loose string away from the drive bolt and the gear case. SPOOL TENSION SPRING 5.
SERVICING YOUR HONDA TRIMMER 9. When you have about 6 inches (150 mm) of line remaining, press the lines into the two notches on the bottom of the spool as shown. This will hold the line on the spool for reassembly. SPOOL I NYLON NOTCHES 10. Guide the ends of the lines through the metal eyelets on the drum. Push the spool into the drum, but be careful not to let any line get trapped outside the edges of the spool. 11.
SERVICING YOUR HONDA TRIMMER Semiautomatic (Bump-Feed) Cutting-Line Head 1. Clean any mud, dirt, debris, etc., from the area around the trimmer head; otherwise, it will make it more difficult to service. 2. Locate the square-shaped“PUSH AND TWIST” button on the side of the trimmer head. TWIST SPOOL COVER 3. Hold the drum section of the trimmer head firmly, then press the “PUSH ANDTWIST” button in slightly, then turn thespool cover slightly to line up the triangle index marks.
SERVICING YOUR HONDA TRIMMER 8. When you have about 6 inches (150 mm) of line remaining, press the linesinto the two notches on the bottom of the spool. This will hold the line on the spool for reassembly. SPOOL NYLON LINE 9. Guide the ends of the lines through the metal eyelets on the drum.Push the spool into the drum; be careful notto let any loose line get trapped outside the edgesof the spool. Hold the spool inside the drum, then place the semiautomatic button and spool cover on top of the spool.
SERVICING YOUR HONDA TRIMMER Removal & Installation . This section shows you how to remove (and install) either style trimmer head from your trimmer. 1. Insert the tip of the 4 mm hexagon wrench (supplied with your trimmer) fully into the hole on the gear case. 2. Turn the trimmer head until you feel the tool drop into the hole in the internal locking ring. Verify the trimmer head does not turn. 3. All drive bolts use left-hand threads.
SERVICING YOUR HONDA TRIMMER Blades Blade Inspection Always wear gloves when working aroundthe blade. Before each use, check the blade for wear and damage, and checkthe tightness of the blade nut. Examine the entire head area, including the debris shield, and clear or clean it free from dirt, debris, loose string, wire, or any other foreign materials. Blade Removal& Installation (UMK431UNBA only) For models other thanthe UMK431 UNBA, a special Barrier Kit must be installed before a blade can be used.
SERVICING YOUR HONDATRIMMER 1. Install the protective plastic cover (that came with the blade) on the blade. 4 mm HEXAGON WRENCH / 2. Insert the tip of the 4 mm hexagon wrench (supplied with your trimmer) fully into the hole on the gear case. 3. Turn the blade until you feel the tool drop into the hole in the internal locking ring. Verify the blade does not turn. The drive bolt and blade nut use left-handed threads.
STORAGE STORAGE PREPARATION Proper storage preparation is essential for keeping your trimmertroublefree and looking good. The following steps will help to keep rust and corrosion from impairing your trimmer’s function and appearance, and will make the engine easierto start when you use the trimmer again. Cleaning Wash the trimmer, including the area around the trimmer head. Wash the engine by hand, and be careful to prevent water from entering the air cleaner.
STORAGE Adding Fuel Stabilizer to Extend Fuel Storage STORAGE PRECAUTIONS Life If your trimmer will be stored with gasoline in the When adding a fuel stabilizer,fill the fuel tank with fuel tank and carburetor, it is important to reduce fresh gasoline. If only partially filled, airin the tank the hazard of gasoline vapor ignition. Select a will promote fuel deteriorationduring storage.
TRANSPORTING BEFORE LOADING If the engine has been running, allow it tocool for at least 15 minutes before loading the trimmer on the transport vehicle. A hot engine and exhaust system can burn you and can ignite some materials. Always turn the ignition switch to the OFF position. Make sure the fuel cap is securely tightened. LOADING The trimmer maybe secured by suitable clamps, hangers orstraps. Secure the trimmer by at least two points along the drive shaft tube.
TAKING CARE OF UNEXPECTED PROBLEMS STARTING PROBLEMS Engine Will Not Start Check control positions. Possible Cause Ignition switch OFF. Choke not in CLOSED (cold engine). Out of fuel. Fuel not reaching carburetor. Bad fuel, trimmer stored without treating or draining gasoline] refueled with bad gasoline. Spark plug faulty, fouled, or has incorrect gap. Fuel filter clogged, carburetor malfunction, ignition malfunction, valves stuck, etc. Check fuel. Remove spark plug.
TAKING CARE OF UNEXPECTED PROBLEMS CUTTING HEAD PROBLEMS Blade or Cutting-line Possible Cause head won’t stop turning when throttle is at SLOW Dosition in throttle control or cable; Check throttle control and cable. throttle cable out of adjustment or bent. Check clutch. BladeorCutting-Line Head Won’t Turn Check clutch,drive shaft, and gearbox. Excessive Vibration Check cutting-line head or blade nut. Check blade. Correction Check throttle control parts, adjust Fault or replace cable if necessary.
TECHNICAL INFORMATION This section contains important information about serial number locations, operation at high altitudes, oxygenated fuels and emissionscontrol systems. Serial Number Locations There are twoserial numbers, one for the trimmer and another for the engine. Record these numbers in the space provided. You’llneed to have these numbers available when ordering parts or making technical or warranty inquires (page 52).
Oxygenated Fuels Some conventional gasolinesare being blended with alcohol oran ether compound. These gasolines are collectively referredto as oxygenated fuels.To meet clean air standards, some areasof the USA and Canada use oxygenated fuels tohelp reduce emissions. If you use an oxygenated fuel, be sureit is unleaded and meets theminimum octane rating requirement. Before using an oxygenated fuel, try to confirm the fuel’s contents. Some states/provinces require this information to be posted on the pump.
TECHNICAL & CONSUMER INFORMATION Emissions Control System Information Problems that may Affect Emissions Source of Emissions If you are awareof any of the following symptoms, have your engine inspected and repaired by your servicing dealer. The combustion process produces carbon monoxide, oxides of nitrogen, and hydrocarbons. Control of hydrocarbons and oxidesof nitrogen is very important because, undercertain conditions, they react to form photochemical smog when subjected to sunlight.
TECHNICAL & CONSUMER INFORMATION Air Index An Air Index Informationhang tag/label was applied to this engine 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.
TECHNICAL & CONSUMER INFORMATIQN Specifications FEATURES Saw blade Length Width Height Dry weight optional; requires optional Barrier Kit Handle installed loop U-type’ loop U-type loop U-type’ loop U-type’ . ’ with saw blade installed 50 DIMENSIONS UMK422K1 I optional; requires optional Barrier Kit I UMK431 K1 Manual feed head: 6.1 5 feet (1.875 m) Semiautomatic feed head: 6.18 feet (1.885 m) 6.27 feet (1.91 m) 13.6 in (345 mm) 23.8 in (605 mm) 10.4 in (265 mm) 13.9 Ib. (6.3 kg) 0 16.
TECHNICAL & CONSUMER INFORMATION single element, semi-dry 3,100 +200 rpm Air cleaner Idle speed I I I FRAME UMK422K1 Engine switch Throttle control Main pipe diameter Main pipe thickness Drive shaft Shaft supportbushings ratio Gearbox type Clutch engagement Clutch type UMK431 K1 Slide type style I trigger motion Two 1.02 in (26 mm) 0.94 in (24 mm) 0.08 in (2.0 mm) 0.06 in (1.5 mm) solid 0.28 in. (7 mm) 7 5 1.33 1.
TECHNICAL & CONSUMER INFORMATIQN CONSUMER INFORMATION Honda Publications Two other documents areavailable from your Honda dealer. Thereis a Shop Manual, whichcovers complete maintenance and overhaul procedures. It is intended to be usedby a skilled technician. There is also a Parts Catalog, that provides a complete, illustrated parts lists. Warranty Service Information Honda Power Equipmentdealership personnel are trained professionals. They should be able to answer any question you may have.
QUICK REFERENCE SECTION r Fuel Capacity Engine oil Capacity Spark plug Carburetor Maintenance Electrode gap Idle speed Before each use First 10 hours Subsequent UMK431K1 UMK422K1 Unleaded gasoline with pump octane rating of 86 or higher (page 31) 0.48 US qVl5.2 fl. oz (0.45 e ) 0.69 US qV22.0 fl. oz (0.65 e ) SAE IOW-30, API SJ (page 27) 0.1 1 US qV3.38 fl.oz (0.1 e ) NGK: CR5HSB DENSO: U16FSR-UB 0.024 - 0.028 in (0.60 - 0.
