Partner Chainsaw Idle Adjustment

For long-term and trouble-free operation, the Partner 351 chainsaw requires periodic inspection and maintenance. Among its modules, the adjustment of which can be handled independently, a carburetor is of paramount importance: the correct setting of this unit is necessary for the effective functioning of the entire mechanism. This article will help to understand its purpose, device and maintenance.

What carburetor is used on a Partner 351 chainsaw

The original Swedish chainsaw of the Chinese assembly Partner 351 is equipped with a Japanese two-stroke carburetor with a built-in fuel pump of the Walbro WT391 diaphragm type. If the ICE power supply unit is replaced by a Chinese counterpart, then the chainsaw has been repaired.

Partner chainsaw idle adjustment

Carburetor device

The purpose of the carburetor of the Partner 351 chainsaw is to prepare and supply the correct fuel-air mixture to the engine.

The carburetor power supply system of the chainsaw engine is arranged according to the standard scheme and includes a fuel pump, a main mixing chamber with a membrane, a throttle and air damper, and three adjusting screws (needles). The aluminum casing provides technological channels for the movement of the air-fuel mixture.

Throttle. a brass plate that controls the amount and speed of air entering through an air inlet with a variable cross-section. Narrowing toward the center and expanding to the opposite edge, as in a venturi, creates a vacuum that traps the fuel on its way to the engine.

The pressure in the main chamber of the carburetor is close to atmospheric, but when the engine starts, a vacuum occurs in the air channels. Opening the damper increases the intensity of the air supply, and with it the force of absorption of the fuel, and the number of working revolutions of the engine.

If the chainsaw starts up tight and stalls, does not produce full power, slowly picks up speed and consumes an excessive amount of gasoline, the carburetor must be adjusted.

Do-it-yourself Partner 351 chainsaw carburetor adjustment

You can cope with the setting of the carburetor of the Partner 351 chainsaw yourself. Its adjustment is made by three screws marked with Latin letters L, H and T. The letter T denotes the idle adjustment screw, H. high speed, L. low.

The tuning process involves two stages: basic and final. The exact angle of rotation must be indicated in the detailed instruction manual for the Partner 351 chainsaw.

To access the carburetor, you need to remove the top cover of the chainsaw Adjusting screws L and H

Basic setting

  1. Tighten screw T clockwise until it stops, then turn back 4.5 turns.
  2. Tighten screws H and L to the end and then turn back 2 turns.
  3. If the engine does not stall at idle, the chain does not move, the engine accelerates quickly and runs smoothly, which means that basic adjustment is enough. If not, fine tuning is needed. A chainsaw should be wound up and warmed up for 5-10 minutes.


  1. Gently turning screw L to one or the other side, find the position at which the revolutions are maximum.
  2. Release screw L a quarter of a circle counterclockwise.
  3. When the chain is idling, screw T to the left until it stops.
  4. If, after tuning, the engine starts poorly or stalls quickly, unscrew screw L another half turn and adjust screw T.

Video: Partner Chainsaw Idle Adjustment

Maximum revolutions

Turn screw H to the right until the maximum speed is reached.

The Partner 351 saw, according to the instruction manual, has a speed limit of 13,000 rpm. Exceeding this indicator is unsafe for the engine and is manifested by characteristic interruptions in ignition and “singing” of ICE, which can be corrected by gradually turning the adjusting screw in the opposite direction.

On a note! The reduction in the number of revolutions under load can be corrected by tightening screw H by approximately 45 degrees.


Pulling the gas trigger of the chainsaw should increase engine speed from idle to maximum power smoothly and quickly. If the set of revolutions is late, screw L must be unscrewed counterclockwise no more than 45 degrees around the circumference.

After setting the acceleration and maximum speed, the operation of the chainsaw should be double-checked at idle.

Repair of the carburetor of the Partner 351 chainsaw (basic malfunctions, their elimination)

Even a very careful and correct carburetor adjustment may not solve some of its malfunctions and the problems caused by them in the operation of the Partner 351 chainsaw. If you cannot restore the normal performance of the ICE power supply unit, it needs to be dismantled, disassembled and repaired.

In some cases, carburetor interruptions are associated with clogged jets, fuel and air filters and, as a result, underfilling of fuel. The main symptoms of this problem are loss of power and unstable engine operation. The cause may be dust, small debris and even water droplets, and water frozen in the carburetor completely blocks the fuel supply channels.

If there is a compressor, all the channels of the carburetor are blown with compressed air, and if the procedure does not help, they are washed in an ultrasonic bath (suitable for jewelry or for washing optics) using a special carburetor liquid. During the cleaning process, the use of metal needles, wire, fleecy or “loose” fabric is prohibited.

Along with the "underfilling" of fuel, its "overflow" is also considered a malfunction.

There are frequent cases when the chainsaw begins to work unstably due to a leak in the seal, which is formed due to a bursting spacer between the carburetor and the chainsaw engine (pictured below). The only way to solve the problem is to replace it with a working one.

Adapter between engine and carburetor of the Partner 351 chainsaw

Why carburetor fills: causes and elimination

In the vast majority of cases, the cause of fuel overflow is a coarse or worn membrane that presses on the beam connected to the needle. But the problem may lie in damage to the needle, valves and levers involved in the operation of the unit. In these cases, a complete analysis of the carburetor is necessary to clarify the cause of the malfunction, and then replace unsuitable consumables.

Before disassembling the carburetor, it is recommended to rinse it with gasoline from the outside, reassembly is carried out only after thorough cleaning, drying and processing with compressed air.

To fix malfunctions associated with fuel overfill, a repair kit for the Partner 351 chainsaw carburetor, which includes all the necessary spare parts and consumables, is useful.


The Partner 351 chainsaw has a serious flaw in the power system, which leads to interruptions in work. This drawback lies in the adapter installed between the engine and the carburetor (we already spoke about this above, the location of the adapter was also noted in the photo).

Over time, a play appears at the junction and the chainsaw begins to suck in air. This malfunction is manifested by a failure at startup (the saw simply does not start), or during operation in the form of instability of revolutions, they spontaneously rise or fall.

The author of the video tells in detail what caused this problem on the Partner 351 chainsaw and how to fix it with your own hands.

Advantages and disadvantages

The main task of engine power tools, in particular, chainsaws, is stable and confident work in any position with respect to gravity. This feature, provided by a diaphragm carburetor with an integrated pump, along with its structural simplicity, is an essential advantage of the Partner 351 ICE power unit.

The disadvantages of the carburetor include the relative complexity of the adjustment, a narrow range of the amount of mixture at the outlet, and slow transitions between steady states. In addition, it is sensitive to accelerations directed perpendicular to the membranes.

Types of carburetors on Partner 351 XT

Partner 351 and Partner 351 XT chainsaws with a slightly more powerful engine have identical WT 391 carburetors, interchangeable with the Walbro models WT 891, W 20, WT 89, WT 324, WT 600, WT 624, WT 637, WT 662, and Zama C1U-W8 and C1U-W14.

The partner 351 chainsaw carburetor, with proper tuning and timely maintenance, provides high tool productivity, turning it into an indispensable assistant on a personal plot, in a garden or at a construction site. By learning to properly regulate the work and eliminate the most likely malfunctions of the "heart" of the internal combustion engine, you can extend the life of the chainsaw and avoid downtime in working with it.