How To Clean A Stihl Trimmer Carburetor

Acceleration check

To test the engine for acceleration, gently press the accelerator and make sure that the engine quickly picks up speed from idle to maximum (from 2800 to 11500-15000 rpm. depending on the brand and model of the saw). If the engine picks up speed slowly, slowly unscrew the screw L counterclockwise (no more than 1/8 of a turn).

Chainsaw ignition system malfunctions

Malfunctions in the ignition system are most often the cause of engine failure in gasoline powered tools. Therefore, you should start troubleshooting with it.

Examine the candle. To do this, carefully remove the high-voltage wire from the head, and then unscrew the candle from the socket using a special key.

If the plug is wet, then there is an excess of fuel. Most often, the supply of an excess amount of fuel is associated with an incorrect carburetor adjustment or with problems in the ignition system.

The candle should be carefully wiped with a dry paper towel and dried. You also need to drain the cylinder, close the fuel supply and start the starter several times to remove excess fuel mixture.

After these steps, you need to install the plug in place, open the fuel supply and try again.

If a lot of black carbon is noticeable on the candle, this usually indicates a malfunction in the fuel supply. a violation of the gasoline / oil ratio, poor-quality oil or the need to adjust the carburetor.

In this case, the candle must be cleaned with a needle or a sharp awl from accumulated carbon deposits, cleaned with a zero sandpaper until a metallic sheen appears and screwed back into place. In this case, you need to pay attention to the tightness of the candle gasket.

If the chainsaw still won’t start, check for a spark in the spark plug. With the cap of the high-voltage wire on, we lean the candle skirt against the cylinder and pull the starter, as shown in the photo below:

If a blue spark jumps from a distance of 2-3 mm, then everything is in order. If the spark appears only at a distance of 0.5. 1 mm, it is most likely that there is a problem with the ignition system. If there is no spark, check the high-voltage cable with a probe. It may have a broken wire.

If all the actions taken did not lead to success, try changing the candle to a known good one and try again to start the chainsaw.

Also, the absence of a spark may be due to a violation of the gap between the ignition module and the flywheel magnetic circuit. The gap should be 0.2 mm. The required gap can be set using a 0.2 mm spacer, which is placed between the flywheel and the ignition module.

The video of the chainsaw ignition device and its malfunction is shown below (to play, press the triangle):

Chain brake

The failure of the chain brake can occur due to contamination of the under-cover space and brake band with sawdust or grease. The wear of the belt also leads to the same. In the first case, you need to clean the lid space, in the second, replace the brake band.

If there is a lawn mower in the household. use, maintenance and repair. to help you. over, you can make a lawn mower yourself from a chainsaw, thus unifying the tool.

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Idle speed adjustment

Before this stage of adjustment, it is necessary to warm up the engine for 5-10 minutes, avoiding high rpm.

Turn the idle speed adjustment screw (T / LA / S) counterclockwise until the engine runs to the minimum rpm. Make sure the chain does not move. That is, if the engine stops idling, turn the idle adjustment screw clockwise. If the chain is in motion, remove the screw counterclockwise.

To complete the adjustment of the chainsaw carburetor, it is necessary to check the engine for acceleration and maximum rpm.

How to adjust a chainsaw carburetor

The chainsaw carburetor is one of the components of the power tool. Many owners of such garden equipment are wondering how to regulate the number of revolutions in their unit. We will give the answer to this question in this article on adjusting the carburetor of a chainsaw.

How to set up a chainsaw carburetor

In general, almost all carburetors, be it a Stihl chainsaw carburetor or a Ural chainsaw carburetor, have three adjusting screws. The screw, designated T, adjusts the idle speed. The L screw controls low rpm and the H screw controls the high rpm, these elements also regulate the fuel / lubricant mixture and air ratio. While tightening the screws clockwise, the carburetor of the Stihl chainsaw is set to low revs, as the fuel mixture becomes leaner. When unscrewing in the opposite direction, the fuel-lubricant mixture is enriched, therefore, the speed increases. The T screw, which is, for example, the carburetor of a husqvarna chainsaw, regulates the idle speed. Turning clockwise increases the idle speed, in the opposite direction decreases.

The basic setting that a chainsaw carburetor undergoes occurs at the factory during the testing of the tool. A more accurate carburetor adjustment is made after the first few hours of operation.

Chainsaw muffler malfunction

It often happens that during prolonged operation, the walls of the exhaust pipe become covered with carbon deposits, which prevents the free exit of exhaust gases.

In this case, remove the muffler (if possible) and wash it with detergents, then dry thoroughly with a hairdryer.

ATTENTION! Carbon deposits contain carcinogens. During dry cleaning, it can enter the lungs and pose a threat to your health.

Carbon deposits are usually caused by an incorrect gasoline-oil ratio or the use of low-quality and incompatible oil.

Carefully read the instruction manual for the chainsaw to prevent this from happening in the future.

Throttle and choke shaft wear

The air and throttle valve shaft can wear out for the following reasons:

• insufficient and improper maintenance of the air filter;
• the air filter is damaged;
• the air filter is not suitable for this unit.

Due to the ingress of poorly cleaned air, the shaft wears out and can break. Broken shaft parts can enter the combustion chamber or crankcase and cause serious damage to the entire piston system.

To eliminate problems with air purification, it is necessary to replace the defective filter or flush the existing (serviceable) one. The filter must be washed in soapy water and dried.

Clogged strainer

The strainer can become dirty if contaminated fuel enters through a fuel hose or a defective pickup head. In the photo below you can see what a clean filter looks like and a dirty one (parts are separated by a line).

Correcting the malfunction will require thorough cleaning and rinsing of the strainer. It is also recommended to blow compressed air through all holes in the carburetor trimmer housing.

Carburetor clean and rebuild on the Stihl FS90R

Fuel pump problems

A common malfunction that “pursues” the fuel pump is the deformation of the pump membrane. For this reason, it does not fit properly and the pump passages are not sealed.

The reasons for membrane deformation can be the following:

• long work of the trimmer;
• use of unsuitable fuel;
• ingress of gases into the impulse channel.

As a result, diaphragm damage reduces pump performance and, as a result:

• depletion of the combustible mixture occurs;
• difficulty starting the engine;
• there are interruptions in the operation of the motor;
• the piston is damaged.

Also, the above-described consequences for the motor can cause clogging of the pump cavity on the impulse side. In this case, dirt enters the membrane through the impulse channel.

To remove the blockage, you will have to disassemble the carburetor and clean the membrane.

Adjustment lever defective

This breakage occurs when the contact surface of the lever wears out.

The abrasion of the contact surface occurs due to the presence of abrasive particles in the gasoline or due to strong vibration of the engine during operation. This defect in the adjusting lever causes problems with the intake, as well as improper idling of the engine.

Common carburetor malfunctions

Failure of the trimmer carburetor occurs due to the use of poor quality gasoline, a damaged air filter and the accumulation of dirt in the chamber of this unit. Most often, it is quite possible to repair the carburetor with your own hands. Listed below are typical lawn mowers carburetor malfunctions.

How the benzotrimmer carburetor works and works

It is almost impossible to cover all types of carburetors produced by manufacturers of gas trimmers. But, since the design of this module, as well as its principle of operation, is largely similar between different models, a generalized description of the processes occurring in the carburetor can be made. This information will allow the user to understand the principles of operation of the device, to eliminate the malfunctions that have arisen and to operate it correctly.

The carburetor trimmer is based on a one-piece aluminum body. Below is a diagram of this block.

At the bottom of it, there is a diffuser, which is also called a Venturi nozzle (18). Air is drawn in by the motor through this nozzle.

The smaller this hole, the faster the air flows, and the higher the level of its vacuum in the zone with the smallest diameter.

In the upper part of the diffuser there are fuel channels (11,12). Through these channels, the air flow draws in gasoline. The fuel pump itself, jets and the system used to regulate the supply of a mixture of fuel with air can be built-in or installed outside.

The throttle valve (9) controls the amount of air sucked into the carburetor. Its amount affects the power that the engine develops. The damper (7) is used for cold starting. It must be closed if you are going to start the unit. After the engine has started, it must be opened, otherwise, the engine will immediately stall.

The impulse channel (1) connects the impulse chamber of the pump to the crankcase of the engine, namely, to its internal volume. The piston located in the cylinder, producing reciprocating movements, successively changes the pressure in the crankcase (vacuum or pressure increase). The pressure drops force the diaphragm (4) to move. Therefore, the pump is synchronized with the engine.

The suction of gasoline from the tank occurs precisely with the participation of the membrane (4). Gasoline enters the carburetor through the union (2). Further, its path lies through the inlet valve (3), the exhaust valve (5), through the strainer (6), the fuel channel (10), passes the needle (14) and fills the chamber (16), which has a control diaphragm (18).

The valve (14) is connected to the diaphragm (18) by means of a lever (17). The cavity, which is located below the membrane, is connected to atmospheric air through the hole (19).

The device functions as follows.

• A vacuum is generated in the diffuser during the suction stroke. This fact causes air leaks. The position of the throttle valve (9) determines the amount of air entering the carburetor chamber, as well as the engine power and the number of its revolutions.
• At this time, fuel is sucked in from the chamber (16) through the jets (11,12), after which it is mixed with the flowing air. Gasoline, mixing with air, begins to spray. Thus, an air-fuel mixture is created.
• The finished mixture enters the cylinder, where it is compressed by the rising piston and ignited at its highest point from the spark generated by the spark plugs.
• Since the volume under the control diaphragm (18) is connected to atmospheric air through the channel (19), the diaphragm moves upward, opening the valve (14) by means of the lever (17). After opening the valve (14), a new portion of fuel enters the chamber (16).
• After the chamber (16) is full, the diaphragm (18) returns to its original position, and the valve (14) closes.

Further, when the motor is running, all the above processes are repeated. A screw (13) is used to adjust the amount of fuel entering the diffuser through the nozzles. The screw (15) is also used to adjust the idle speed. When the regulators are twisted, the fuel mixture is enriched, and when the regulators are twisted, the mixture becomes lean. Also, in some carburetor models, you can adjust the idle speed of the engine with a quantity regulator. It is usually located outside and, when twisted, rests against a lever attached to the throttle shaft.

Thus, using 3 adjusting screws, you can achieve maximum performance of the engine, as well as adjust its smooth operation at any ambient temperature, and even in mountainous areas.

Intake Adjuster Lever Problem

This problem can occur if the adjusting arm is not properly installed or if it bends before installing. As a result, the contact surface takes the wrong position, which disrupts the additional fuel supply.

Clogged control cavity

If dirt accumulates in the control cavity, the inlet needle cannot close the hole tightly and a lot of fuel pours into the chamber.

This causes the fuel to over-enrich and the engine starts to malfunction. It is necessary to disassemble the carburetor and clean the cavity of the adjusting membrane.