Partner 340 Chainsaw Carb Adjustment

Partner 340c chain saws (Partner 340s) are equipped with reliable carburetors, which almost do not break and do not require periodic maintenance. But, during operation, sometimes there is a need for its adjustment. This is where the knowledge required in this article will be required. from the device, to the step-by-step carburetor tuning with your own hands.

What carburetor is used on a Partner 340 chainsaw

The Partner 340s chainsaw is equipped with a membrane carburetor of the Japanese company Walbro. It is quite reliable and unpretentious in operation. To facilitate winter start-up, a primer is installed in the carburetor (fuel pump).

Partner 340 Chainsaw Carb Adjustment

Carburetor device

The carburetor body of the Partner 340 chainsaw is made of aluminum alloy. It has technological channels through which the mixture of fuel with oil and a diffuser move. The task of the latter is to mix air with gasoline, thereby forming a combustible mixture.

The main elements of the carburetor include:

  • fuel pump;
  • main chamber with a membrane;
  • throttle and air flaps;
  • screws (adjusting quality, quantity, idle);
  • needle valve;
  • fuel jets.

DIY carbide adjuster for Partner 340 chainsaw

Initially, the Partner 340 chainsaw carburetor was adjusted by the manufacturer to operate in maximum power and economy mode. Additional adjustment may be necessary in case of deterioration in traction characteristics, which is possible with sudden changes in air temperature or when pouring other fuel into the tank.

Before adjustment, it is necessary to clean the chainsaw carburetor from dust and dirt (it is better to use a compressor with an air nozzle for these purposes).

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The carburetor adjustment algorithm itself is as follows:

  1. To access the quality screws (marking H) and quantity (L) on the chainsaw there are special holes on the left side. For convenience, you need to remove the protective cover.
  2. We tighten both screws to the end, and then unscrew each one 1/5 turn.
  3. We start the chainsaw and warm up the engine for 5-10 minutes.
  4. We configure idling. To do this, screw the screw T counterclockwise until the engine starts to work as steadily as possible. At the same time, make sure that the chain does not rotate (if it rotates, gently tighten the screw until it stops). If the engine stalls at idle, screw T must be loosened again a little.
  5. We adjust the motor power and the quality of the mixture. By gently pressing on the gas, we are waiting for the engine speed to grow to a maximum. According to the manufacturer, the maximum speed is 11.5 thousand rpm (for accurate determination, use a portable electronic tachometer). If the speed does not increase, turn the screw L counterclockwise 1/8 turn. Do not exceed the maximum speed above the recommended, because this may cause ignition problems. In this case, turn the screw H counterclockwise, thereby reducing the maximum speed

Video: Partner 340 Chainsaw Carb Adjustment


If there is no tachometer at hand, you can determine whether the carburetor is visually tuned correctly. When the motor smokes a lot during operation (the mixture is enriched), screw L must be tightened a little. In the case when the engine is warming up and gaining speed itself, screw H must be loosened counterclockwise by approximately ΒΌ turn.

Sometimes it happens that the adjustment does not help. The motor does not develop speed or stall. The cause may be a clogged filter or air intake. It is enough to clean and adjust the carburetor again if necessary.

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Repair of the carburetor of the Partner 340 chainsaw

A frequent malfunction of the carburetor of the Partner 340 chainsaw is associated with a fuel leak (loss of tightness). First you need to check the integrity of the gasket between the carburetor and the crankcase. If everything is in order with her, then the matter is the tightness of the carburetor.

To check the tightness you will need a manometer. The inlet of the meter is put on the fuel supply hose. Then, using a pear, a certain amount of air is pumped into the carburetor. Instrument readings must comply with at least 0.4 bar. After some time, the pressure is measured again. If it falls, the carburetor needs repair. The reason for this may be the following reasons:

  • malfunction of the control diaphragm (in the main chamber) or the fuel pump diaphragm. The tightness here is broken due to the loss of the shape of the membranes or the appearance of holes on them. This problem occurs due to prolonged operation or carburetor overheating;
  • the needle does not completely close the valve, as low-quality fuel contributes to its clogging. In addition, the geometry of the needle cone changes over time due to wear. To this we add the insufficient mobility of the lever of the needle valve on its axis when it is worn or bent. And its spring has lost its elasticity.
  • the plane of the flap valves in the fuel pump is disrupted. As a result, they are poorly pressed against the supporting plane and, as a result, the carburetor is not tight (the pump loses productivity).

On the side of the carburetor of the Partner 340 chainsaw, a membrane chamber cover is installed. Through the hole in it, dirt gets into the carburetor. When it accumulates, the membrane rises and pushes the needle valve lever. As a result, the lever does not completely block the fuel channel, which leads to re-enrichment of the mixture.

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It is necessary to remove and clean this cover from accumulated dirt more often. Fortunately, its design allows you to do this easily and quickly (you need to unscrew the four screws on the side of the carburetor).

All of the above malfunctions, as a rule, have 2 main causes: engine overheating (poor mixture) and carburetor clogging (insufficient fuel cleaning). Both problems are solved by the correct setting and timely cleaning of the carburetor, air filter. Do not forget about the high-quality filter element for gasoline.

Particular attention when cleaning should be given to the grid, its smallest clogging leads to unstable operation of the chainsaw.

Failed parts can be replaced by purchasing the appropriate repair kit.

Carb repair video

The author of the video first shows how the problem manifests itself (conducts trial runs of the chainsaw), and then performs step-by-step analysis, cleaning and tuning of the Partner 340 carburetor. Everything is explained in detail and in an accessible language.

To summarize

The carburetor of the Partner 340s chainsaw has no significant drawbacks. It is simple and reliable in design. All breakdowns in it occur due to careless operation of the chainsaw and prolonged use (material fatigue). Proper adjustment and maintenance of the carburetor will significantly extend its service life. Someone may not be happy with the average cost of a carburetor. 23-30 However, in this case, the price is quite consistent with the quality.