How To Clean Carborator On Husqvarna 440 Chainsaw

Husqvarna 435, 435E and 440E chainsaw carburetor adjustment, removal and refitting guide will assistance with any carburetor cleaning, replacement, inspection and correct running of the chainsaw. A Service Manual detailing the Carburetor removal and refitting procedures with full diagrams, every bit well equally more complete chainsaw repair data, is bachelor to download. Likewise a Husqvarna and 435, 435e and 440e Parts List, Operator Manual, and Zama carburetor manual are also available to view or download every bit a PDF which tin can be read on any device or easily printed.

Carburetor for Husqvarna Chainsaw 435, 435E and 440E

Fig 22

These prove the principle for the design and function of the carburetor.

Design

The carburetor is based on 3 sub-systems:

• • The metering unit, A.
  • The mixing venturi, B.
  • The pump unit of measurement, C.

The jets and the fuel'due south control functions are located in the metering unit of measurement (A). Here the correct quantity of fuel is adjusted for the actual speed and ability output (see figure 22).

Fig 23

The mixing venturi (B) houses the asphyxiate, throttle valve, and diffuser jets. Here the air is mixed with the fuel to give a fuel/air mixture that can be ignited by the ignition spark (see figure 23).

In the pump unit (C), fuel is pumped from the fuel tank to the metering unit. One side of the pump diaphragm is connected to the crankcase and pulses in fourth dimension with the pressure changes in the crankcase. The other side of the diaphragm pumps the fuel (run across figure 24).

Fig 24

Function

Fig 25

The carburettor operates differently in the following modes:

• Common cold starting time mode
• Idling style
• Part throttle way
• Full throttle style

In the cold start style (run into figure) the choke valve

(H) is fully closed. This increases the vacuum in the carburettor then that fuel is sucked more easily from all the diffuser jets (D, E, and F). The throttle valve (I) is partly open up. Extra air inlet (J) is closed (see figure 25).

Fig 26

In the idling mode (run across figure) the throttle valve (I and J) is closed and the choke valve (H) is open.

Air is sucked in through an aperture in the throttle valve and a small amount of fuel is supplied through the diffuser jet (D) (see figure 26).

In the part throttle mode (see figure beneath) the throttle valve (I) is partially open and the choke valve

Fig 27

1. is open. Fuel is supplied through the diffuser jets (D and East). The throttle valve (J) starts to open up (see figure 27).

In full throttle mode (run into figure beneath) all valves are open up and fuel is supplied through all diffuser jets (D, E, F, and G). Extra air inlet (J) is likewise fully opened (run across figure 28).

Fig 28

Dismantling the carburetor

Fig 29

• 1. Dismantle the cylinder comprehend and the air filter.
  2. Disassemble the handle holder (see figure 29).
  3. Push the throttle actuator rod out of the handle part. Unhook it from the carburettor (see figure thirty).

Fig 30

• 1. Remove the return hose (B) and suction hose (C). Loosen the fuel pump (D). Let the fuel hose (Chiliad) remain in place (see figure 31).

Fig 31

Annotation!

Have care when lifting out the carburetor and then that the fuel hose does not become loose.

• 1. Loosen the screws (Due east) and unhook the rubber mountings (F) (run into figure 32).

Fig 32

• 1. Disassemble the pump cover (G) over the measuring sleeping room comprehend (R) and carefully remove the control diaphragm (H) with gasket (J).

Fig 33

• 1. Unscrew the screw (M) and remove the needle valve (50) with the lever (M), shaft (Due north) and leap (P).
  2. Unscrew the spiral (Q) above the pump unit of measurement and carefully remove the gasket (S) and diaphragm (T).
  3. Employ a needle or similar device and carefully pull up the fuel screen (U).
  4. Unscrew the high (V) and low jet screws (Due west) (see figure 34).
  5. If necessary, dismount the throttle valve (X), choke valve (Z) and air shutter (Y) and remove the shafts with levers and springs (run into

figure 34).

Cleaning and inspection

Clean all units in clean petrol.

Utilize compressed air to dry the petrol on the components. Direct the air through all channels in the carburetor housing and ensure that they are not blocked. Check the following:

• • 1. That gaskets, pump, and control diaphragms are undamaged.
    2. That in that location is no play on the throttle and choke valve shafts.
    3. That the needle valve (L) and its lever (M) are not worn (see figure 33).
    4. That the fuel screen (U) is whole and clean (see figure 33).
    5. That the tips of the loftier (5) and low jet screws

(W) are non damaged (run into figure 34).

• • 1. That the intake manifold (R2) is undamaged (meet figure 33).
    2. The carburetor has an extra air shutter connected in parallel with the ordinary throttle valve.

Fig 34

Associates

Fig 35

Maintain a high level of cleanliness when assembling the carburetor. The slightest contamination can upshot in running problems.

1. If the throttle and choke valves, together with levers and springs were removed, they should exist refitted. The jump is tensioned 1-ii turns. Lubricate the shaft bearings with light oil.
2. Fit the high (V) and low (Due west) speed needles and springs. Note! Practise not fully tighten the screws. This will harm the seats and needle tips.
3. Fit the fuel filter (U) past using the handle of a small-scale screwdriver. (see figure 33)
4. Fit pump encompass (Thou), gasket (S) and measuring chamber cover (R) over the pump unit (see figure 33).
5. Fit the needle valve (L) with the lever (M), shaft (North) and spring (P) and tighten the spiral (Grand). Fit the expansion washer (F) (see figure 35).

Fig 36

1. Cheque using a ruler or the similar that the lever is level with the assembly airplane on the cover. The lever arm can exist bent if necessary (see figure 36).
2. Fit the control diaphragm (T) with gasket (S) and measuring chamber embrace (R) over the metering unit (see figure 37).

Fig 37

1. Printing in the screen (U). Fit the measuring bedchamber comprehend (R) and tighten the screw (Q) (meet figure 37).
2. Put together the gasket (J) and control diaphragm (H) and press up (see figure 37).
3. Assemble all the parts and tighten the iv screws (see figure 37).

11.. Acquit out a pressure exam.

Pressure testing the carburetor

Fig 38

Pressure testing should be carried out with the carburetor fully assembled. Testing should always exist carried out after the carburetor has been repaired, merely it can also be carried out as troubleshooting before dismantling the carburettor.

Encounter figure and behave out the exam as follows:

1

Set the high and low jet screws 2 turns from the lesser.

2

Connect force per unit area tester to the carburettor's fuel intake.

three

Lower the carburettor into a beaker of water (see figure 37).

iv

Pump the pressure upward to 50 kPa.

5

No leakage is permitted. If a leakage occurs refer to the tabular array below.

Leakage at	Mistake with
Diffuser jets Leakage in impulse tube Ventilation pigsty on the metering unit.	Needle valve Pump diaphragm Command diaphragm

Assemble on the saw

Fig 39

1. Press the carburettor down towards the partition wall. Make sure that it gets into the correct position.
2. Fit the filter holder by hooking the choke control into the choke lever (A).
3. Hook on the rubber mountings. Insert and tighten the screws.
4. Insert the return hose (B) into its position in the filter holder.

Fig 40

1. Printing on the fuel diaphragm (D). Fit the suction hose (C) and return hose (B).
2. Hook in the throttle actuator rod into the carburetor. Thread the handle holder into the throttle actuator rod (A). Push the rod forwards so that information technology tin can be inserted into the handle role.

Fig 41

1. Push button downwards the handle holder into the filter holder (run across figure 42).
2. Assemble the air filter and cylinder encompass.

Fig 42

1. Mount the handle holder.

Carburettor adjustment Conditions during adjustment

Fig 43

• • The air filter should be clean and the cylinder comprehend fitted when adjustments are made. Adjusting the carburettor with a dirty air filter will requite a also lean fuel mixture the side by side fourth dimension the air filter is cleaned. This can result in serious damage to the engine.
  • Mountain, for this model, approved bar and chain combination (see Technical data in the Operator's Manual).

435/e xvi″

440e sixteen″

• • The chain should non be tensioned more than that it remains ~ 0,2 inches to the bar.

(See figure 43)

Fig 44

Replacement of the H-needle or complete carburetor

1. Carefully screw the new H-needle to the bottom and turn it anticlockwise "A" turns.

435/eastward A = ii

440e A = two

1. Start the engine. If necessary, adjust the idling speed with the T-screw until the chain stops.
2. Adjust the H-needle to give a top speed of "B" rpm. Use a tachometer.

435/e B = 12500 -13 000, speed limitation 440e B = 12500-thirteen 000, speed limitation

Use screwdriver 530 03 55-threescore.

1. Let the engine run at "B" rpm ~ 1 infinitesimal, until warm.

Replacement of the L-needle

one. Spiral the new L-needle to the bottom and then plow it counterclockwise "D" turns.

435/e D = 2,5

440e D = 2,5

(Encounter figure 44)

Husqvarna 435, 435e, 440e Carburetor Adjustment and Repair

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