Husqvarna How to Adjust Carburetor and Idle on Chainsaws: A Comprehensive Guide
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Repair instructions

Carburettor – adjustment

For instructions on adjusting the EPA carburettor see appendix A.

Adjusting the carburettor involves adjusting the engine to the local conditions e.g. climate, alti- tude, fuel and type of two-stroke oil.

The carburettor is equipped with three adjustment options.

L = Low speed jet

H = High speed jet

T = Idling adjustment screw

The L and H jets adjust the fuel flow to match the airflow that the throttle valve opening allows. Turning them clockwise makes the fuel/air mixture weaker (less fuel in relation to the amount of air) and turning them anti-clockwise makes the fuel/air mixture richer. A weak mixture increases the engine speed and a rich mixture decreases the engine speed.

The T screw controls the throttle position when idling. Turning the T screw clockwise gives faster idling; turning it anti-clockwise lowers idling speed.

WARNING!

The guide bar, chain and clutch cover must be fitted before the saw is started, otherwise the clutch may fly off and cause inju- ry.

Basic settings and running in

During testing at the factory the carburettor is adjusted to the basic factory settings.

The factory settings are H = 1 turn and L = 1 turn.

To ensure that engine components receive adequate lubrication (running in) the carburet- tor should be set to a somewhat richer fuel mixture for the chainsaw’s first 3-4 running hours. This is done by adjusting the maximum speed to 6-700 rpm less than the recom- mended maximum speed.

If it is not possible to check the maximum speed with a tachometer then the H jet should not be set to a weaker mixture than the basic factory setting.

The recommended maximum speed must not be exceeded.

NOTE!

If the chain turns at idling speed, the T screw should be turned anti-clockwise until the chain stops.

Fine adjustment

Once the chainsaw is “run in” the carburettor should be readjusted. First adjust the L jet screw, then the idling screw T and finally the H jet screw.

The recommended engine speeds are as follows:

Model

Max revs

Idle revs

340

12,500 rpm

2,700 rpm

345

12,500 rpm

2,700 rpm

346XP/G

14,200 rpm

2,700 rpm

350

13,000 rpm

2,700 rpm

350 EPA

13,000 rpm

2,700 rpm

351

13,000 rpm

2,700 rpm

353

13,000 rpm

2,700 rpm

Basic requirements

•Before making any adjustments the air filter should be clean and the cylinder cover should be in place. If the carburettor is adjusted with a dirty air filter, the mixture will be too weak next time the air filter is cleaned. This can cause serious engine damage.

•Carefully screw in the L and H jets fully, then back them off 1 turn. The carburettor now has the settings H = 1 and L = 1.

•Start the chainsaw and allow it to warm up for 10 minutes.

•Place the saw on a flat surface so that the guide bar is pointing away from you and the guide bar and chain are not touching the surface.

Low speed jet L

•Find the highest idling speed by slowly screwing the L screw in and then out again.

•When the highest speed has been found, screw out the L screw 1/8 - 1/4 turn.

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Contents 340 345 346XP 350 351 Workshop manual Husqvarna 340/345/346XP/350/351/353 Contents Appendix A, Carburettor EPA modelsArrangement of the manual TroubleshootingIntroduction Construction and functionSpecial instructions Safety regulationsGeneral instructions Special tools 20 b 20 c 20 aTechnical data Rpm Construction and function CarburettorConstruction and function Idling low rpm TroubleshootingStarting High rpm Acceleration and retardationChain brake dismantling Cleaning and inspectionRepair instructions Chain brake reassembly Operating testSilencer refitting Chain catcher replacementSilencer removal RefitStop switch removal Stop switch resistance measurementStop switch refitting Choke control removalThrottle lock, throttle trigger and return spring refitting Choke control refittingThrottle lock, throttle trigger and return spring removal Hand grip heater on model 346XPG, 351G, 353G removal Generator troubleshootingSwitch troubleshooting Troubleshooting carburettor heater 346XPG, 351G, 353G Heater element and rear hand grip removal Hand grip heater on model 346XPG, 351G, 353G refittingStarter assembly removal Replacing a broken or worn starter cordReplacing a worn recoil spring Starter assembly refittingTensioning the recoil spring Model 346XP, 351 Ignition module testingIgnition module/flywheel removal Replacing the generator, model 346XP, 351 Generator refittingIgnition module and flywheel refitting Centrifugal clutch refitting Inspection and cleaningCentrifugal clutch removal Oil pump removal 346XP, 350, 351 ModelOil pump removal 340 Oil pump -refitting 346XP, 350, 351Oil pump -refitting 340 Adjustable oil pump adjustment 346XP, 350, 351 Carburettor removalCarburettor dismantling On saws with a carburettor heater 346XPG, 351G, 353GCarburettor reassembly On saws with a carburettor heater 346XPG, 351G, 353G Carburettor pressure testingCarburettor refitting Carburettor heater 346XP, 351, 353 Refitting Air intake system removal Air intake system refitting Low speed jet L Carburettor adjustmentBasic requirements Fuel tank removal Fine adjustment of idling speed TCarburettor correct adjustment High speed jet HReplacing the fuel filter Replacing the fuel hoseTank vent testing Fuel tank refittingIf replacing the cylinder Piston and cylinder removalModels 340 Decompression valve pressure testing Piston and cylinder refitting 346XP, 350, 351 Cylinder pressure testing Piston and cylinder refitting 340Crankcase and crankshaft dismantling 346XP, 351 Sealing ring replacement drive side Crankshaft bearings replacement 346XP, 351Sealing ring replacement Crankshaft complete dismantling 340, 345Take care to avoid damaging the crank- case Crankshaft bearings 340, 345, 350 replacementCrankcase and crankshaft reassembly 346XP, 351 Crankshaft complete 340, 345, 350 reassembly Thread insert Repairing damaged threadsGuide bar bolts replacement Check that Basic adjustment for EPA II carburetorsReplacement of the L-needle H-needle must not rotate114 01 2003W12

340, 345, 346XP,350, 351, 353 specifications

Husqvarna is renowned for its high-quality chainsaws, and the Husqvarna 340, 345, 346XP, 350, 351, and 353 models are no exceptions. These models have garnered a reputation among both professional and amateur users for their reliability, durability, and cutting performance.

The Husqvarna 340 is an entry-level model designed for homeowners and light-duty tasks. It features a 40cc engine that provides a good balance of power and weight, making it easy to handle during extended use. The 340 is equipped with low-vibration technology, significantly reducing operator fatigue and making it suitable for less experienced users.

The Husqvarna 345 is slightly more powerful than the 340, boasting a 45.7cc engine. This model is ideal for users who require a bit more power for medium-duty tasks. It incorporates the air injection system, which helps to separate larger debris before it reaches the air filter, prolonging the life of the filter and maintaining optimal performance.

Moving up the range, the Husqvarna 346XP is a powerful professional chainsaw tailored for demanding tasks. With a 50.2cc engine and the X-Torq engine technology, it provides high cutting performance while reducing fuel consumption and emissions. The 346XP features an adjustable oil pump that allows for precise lubrication, making it an excellent choice for commercial users.

The Husqvarna 350 shares similarities with the 346XP but is designed for users who need a well-rounded saw for various applications. Its 50.2cc engine delivers ample power, and the ergonomically designed handle provides comfort during prolonged use. The chainsaw's advanced starting system ensures easy ignition, even in challenging conditions.

The 351 is another versatile option, equipped with a 50cc engine, designed for both professional and home use. It emphasizes user comfort and ease of handling. The compact design combined with features such as an efficient air filtration system makes the 351 suitable for long hours of work.

Lastly, the Husqvarna 353 is a heavy-duty model that excels in performance and longevity. It has a 50cc engine and incorporates various safety features, including a chain brake and throttle lock, to ensure safe operation. The saw also utilizes the unique anti-vibration system, minimizing vibrations that can lead to user fatigue.

In summary, the Husqvarna 340, 345, 346XP, 350, 351, and 353 models each offer distinct features catering to a wide range of users. From homeowners tackling light tasks to professionals requiring rugged performance, these chainsaws showcase Husqvarna's commitment to quality, innovation, and user-centric design.
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