Husqvarna 340, 345, 346XP,350, 351, 353 manual Construction and function, Carburettor

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Construction and function

Carburettor

The carburettor consists of three sub-systems:

•The metering unit (A) which contains the jets and the fuel control mechanism. This measures out the right amount of fuel to suit the speed of the saw and the power demand.

•The mixing unit (B) consists of the choke, diffuser jets and throttle valve. This is where the air and fuel are mixed to create a flammable mixture.

•The pump unit (C) pumps fuel from the tank to the metering system inside the carburettor. One side of the pump diaphragm is connected to the crankcase and pulses as a result of pressure changes in the crankcase. The other side of the diaphragm sucks in the fuel.

The carburettor works in different ways depending on the setting:

•Cold start mode

•Idling mode

•Part throttle mode

•Full throttle mode

In the cold start mode the choke valve (D) is completely closed. This increases the vacuum in the carburettor so that fuel is sucked through the diffuser jets faster (E).

In idling mode the throttle valve (F) is closed. Air is sucked through an aperture in the throttle valve and a small amount of fuel is supplied through the diffuser jet (E).

8 – English

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Contents 340 345 346XP 350 351 Appendix A, Carburettor EPA models Workshop manual Husqvarna 340/345/346XP/350/351/353 ContentsIntroduction TroubleshootingArrangement of the manual Construction and functionSafety regulations General instructionsSpecial instructions Special tools 20 a 20 b 20 cTechnical data Rpm Carburettor Construction and functionConstruction and function Troubleshooting StartingIdling low rpm Acceleration and retardation High rpmCleaning and inspection Repair instructionsChain brake dismantling Operating test Chain brake reassemblySilencer removal Chain catcher replacementSilencer refitting RefitStop switch resistance measurement Stop switch removalChoke control removal Stop switch refittingChoke control refitting Throttle lock, throttle trigger and return spring removalThrottle lock, throttle trigger and return spring refitting Generator troubleshooting Switch troubleshootingHand grip heater on model 346XPG, 351G, 353G removal Troubleshooting carburettor heater 346XPG, 351G, 353G Hand grip heater on model 346XPG, 351G, 353G refitting Heater element and rear hand grip removalReplacing a broken or worn starter cord Starter assembly removalStarter assembly refitting Tensioning the recoil springReplacing a worn recoil spring Ignition module testing Ignition module/flywheel removalModel 346XP, 351 Generator refitting Replacing the generator, model 346XP, 351Ignition module and flywheel refitting Inspection and cleaning Centrifugal clutch removalCentrifugal clutch refitting Model Oil pump removal 346XP, 350, 351Oil pump -refitting 346XP, 350, 351 Oil pump removal 340Oil pump -refitting 340 Carburettor removal Adjustable oil pump adjustment 346XP, 350, 351On saws with a carburettor heater 346XPG, 351G, 353G Carburettor dismantlingCarburettor reassembly Carburettor pressure testing Carburettor refittingOn saws with a carburettor heater 346XPG, 351G, 353G Carburettor heater 346XP, 351, 353 Refitting Air intake system removal Air intake system refitting Carburettor adjustment Basic requirementsLow speed jet L Carburettor correct adjustment Fine adjustment of idling speed TFuel tank removal High speed jet HReplacing the fuel hose Replacing the fuel filterFuel tank refitting Tank vent testingPiston and cylinder removal Models 340If replacing the cylinder Decompression valve pressure testing Piston and cylinder refitting 346XP, 350, 351 Piston and cylinder refitting 340 Cylinder pressure testingCrankcase and crankshaft dismantling 346XP, 351 Sealing ring replacement Crankshaft bearings replacement 346XP, 351Sealing ring replacement drive side Crankshaft complete dismantling 340, 345Crankshaft bearings 340, 345, 350 replacement Crankcase and crankshaft reassembly 346XP, 351Take care to avoid damaging the crank- case Crankshaft complete 340, 345, 350 reassembly Repairing damaged threads Guide bar bolts replacementThread insert Replacement of the L-needle Basic adjustment for EPA II carburetorsCheck that 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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