Trimmer Adjustment

Adjustment and repair of the carburetor lawn mowers Instructions for adjusting the carburetor lawn mowers.

Adjusting and repairing the carburetor lawn mowers

The trimmer does not belong to complex household appliances, therefore most of its breakdowns are mechanical in nature and are quite successfully eliminated with their own hands. Even if the engine fails for serious reasons, damage to the piston ring, for example, repairs are reduced to replacing a part.

But even with a relatively simple design, such a part of the device as the carburetor needs to be adjusted.

trimmer adjustment

Principle of operation

The carburetor is a power system module in which liquid fuel and air are mixed before being fed into the engine cylinders. Mixing and feeding are adjusted accordingly depending on the tool and its mode of operation.

The carburetor device for lawn mowers is the same for almost all cases. It belongs to the category of float devices. The latter provide stable parameters of ready-made mixtures.

The principle of the module is as follows.

  • Air enters the body of the air damper tube. The latter increases or decreases the air flow depending on its position.
  • In the area where the gasoline feed hole is formed, the tube has a narrowing diffuser. Here the flow rate increases.
  • Fuel from the float chamber is fed through the nozzle into the tube. The float level determines the amount of fuel supplied. Since the pressure in the chamber is normal, and in the tube it is low due to the greater rarefaction of the air, gasoline is sucked in through the nozzle.
  • The accelerated air flow picks up the fuel and sprays it, forming an air-fuel mixture of the desired density.
  • The mixture is sucked into the cylinder through the pipeline.

The more open the air damper in the tube, the higher the density of the air flow, which means more fuel enters the cylinder. Adjusting the carburetor of lawn mowers is reduced to setting such a ratio of flaps, at which the density of the fuel mixture becomes optimal.

Signs of imbalance

Debugging the carburetor must be done during the manufacture of the device. As a rule, the owners will learn about the need to adjust the fuel supply with their own hands only after serious enough breakdowns, in the process of correcting which, the module was removed and, for example, cleaned.

Signs of a configuration failure are the following:

  • Starts, but the engine immediately stalls because the engine can only work when a certain amount of gasoline is supplied, with too lean fuel, that is, blocking the supply channel, the engine will stop;
  • Too high fuel consumption, a lot of exhaust gases are the result of incomplete combustion of the mixture. In this case, on the contrary, there is too much fuel and the mixture is too dense.
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Adjusting the idle trimmer

Location of carburetor adjustment screws

The T (AT) screw serves as a limiter for the reciprocating movement of the fuel flap and when it is tightened, the engine rpm increases, and loosening leads to a decrease in the engine speed. Professionals advise adjusting the idle screw of lawn mowers so that the internal combustion engine runs a little faster at minimum speed, but the head with a fishing line or knife remains stationary. If after these manipulations it is difficult to start the trimmer to cold, then it is enough to tighten the screw T a quarter of a turn and try to start the engine again.

Carburetor Trimmer Adjustment

The initial step in restoring the correct operation of the fuel system is to clean the air filter.

Trimmer carburetor with screws

Experts recommend rinsing it in a solution of water and detergents after every 10-15 hours. Direct adjustment of the carburetor trimmer is done with three adjusting screws:

  • Fuel adjustment screw (L);
  • High speed adjustment screw (H);
  • The screw responsible for the engine idling (T or AT).

Carburetor Adjustment Lawn Mowers Highlights

Despite their high productivity, mobility and unpretentiousness in work, modern lawn mowers can hardly be attributed to complex devices. Over time, any mechanism is subject to wear and tear, and therefore parts and assemblies require special attention from the owner. One of these trimmer elements is the carburetor, designed to form a fuel mixture and feed it into the combustion chamber. Increased fuel consumption with proper observance of the proportions of gasoline and oil or a drop in engine power indicate the need to adjust the carburetor of the gasoline trimmer.

Adjusting the fuel supply at minimum speed

Before you start tuning the carburetor of the petrol trimmer, you need to warm up the engine to operating temperature.

Fuel adjusting screws

To do this, we start the internal combustion engine and, at idle, let it run for 10-15 minutes. In the first step, with the trimmer running, slowly tighten screw L until intermittent operation starts or until it stalls. Next, unscrew the screw ¼ of a turn and check the maximum speed set. If the lawn mower reaches high revs quickly and easily, this will be the most economical mode. In most of the models on the market, the fuel screw L is turned clockwise, however, there are trimmers where the decrease and increase in the mixture flow occurs in the opposite order.

Adjusting the idle trimmer

Location of carburetor adjustment screws

The T (AT) screw serves as a limiter for the reciprocating movement of the fuel flap and when it is tightened, the engine rpm increases, and loosening leads to a decrease in the engine speed. Professionals advise adjusting the idle screw of lawn mowers so that the internal combustion engine runs a little faster at minimum speed, but the head with a fishing line or knife remains stationary. If after these manipulations it is difficult to start the trimmer to cold, then it is enough to tighten the screw T a quarter of a turn and try to start the engine again.

Carburetor Trimmer Adjustment

The initial step in restoring the correct operation of the fuel system is to clean the air filter.

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Trimmer carburetor with screws

Experts recommend rinsing it in a solution of water and detergents after every 10-15 hours. Direct adjustment of the carburetor trimmer is done with three adjusting screws:

  • Fuel adjustment screw (L);
  • High speed adjustment screw (H);
  • The screw responsible for the engine idling (T or AT).

Spring may interfere

My first attempt to adjust the carburetor of the lawn mowers did not work, as the spring of the screw for adjusting the fuel mixture interfered with. The factory spring turned out to be too thick when compressed and did not make it possible to reduce the fuel supply to the required level. I had to pick up another spring and continue adjusting after replacing it.

Fuel mixture adjusting screw with spring

In the photo above the factory spring, below the adjusting screw with the matched spring. I am writing about this because I’m not sure if this is an isolated case, and someone else may face the same situation.

Lawn mower or trimmer

A trimmer is a broader concept than a lawn mower (lawn mower), as it can also be electric. A petrol trimmer and a lawn mower are the same thing.

Some authors claim that the trimmer is a weaker tool than a more powerful lawn mower, which can be used for mowing shrubs. Personally, I have a tool with a maximum power of 1.7 kW and is capable, as stated in the instructions, of mowing small shrubs up to 10 mm thick. The user manual is called Petrol Trimmer.

Carburetor adjustment

Flush the air filter before adjusting the carburetor. It is recommended to rinse it after every 10 hours of operation. After that, you can start adjusting. The photo shows the PRORAB-8406 petrol trimmer carburetor as an example. The numbers indicate the adjusting screws that we will use.

PRORAB-8406 petrol trimmer carburetor adjusting screws

Purpose of adjusting screws:

  1. Fuel mixture adjustment screw.
  2. Idling adjustment screw.
  3. Maximum speed limiting screw.

Start a lawn mower and wait for it to warm up.

Find the highest idle speed by slowly turning the screw to the left or to the right. After finding the maximum rpm position, turn the screw counterclockwise на turn.

Note: FORTE lawn mowers are shipped from the factory with the right screw completely unscrewed (0.5 turn). At this stage, he should be looking at 11 o’clock.

Bottom screw T. Responsible for adjusting the engine idle speed. Turning the screw counterclockwise decreases the number of revolutions. Counterclockwise increases.

Carburetor adjustment FORTE lawn mowers

The gasoline lawn mower has been successfully used for a long time in a variety of industries: for lawn maintenance in private plots, in housing and communal institutions, landscaping organizations, agriculture and forestry. The main competitive advantages of the products. Low maintenance costs, increased reliability and ease of use.

Engine. The most important component of any technique. And so that it always works in the optimal mode for itself, it is recommended to fine-tune the carburetor.

How to repair the carburetor of lawn mowers with your own hands and why do they recommend doing this? First of all, to make sure that the engine is working properly and that the maximum productivity of the tool is ensured 100%.

FORTE Lawn Mowers Carburetor Setting:

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1. Start the engine of the device and let it warm up for 10 minutes (if you observe the rotation of the cutting element at idle speed, turn the idle screw in the opposite direction, turn until the spool stops turning).

2. Gently rotate the right and left needles to the middle position. Important! Never twist the stopper; this may damage the engine).

3. There are 3 adjusting screws to adjust the carburetor:

  • Right H low speed screw
  • Bottom T screw idle
  • Left L high speed screw

Right screw H. First of all, the low speed screw is adjusted.

Correct adjustment is considered only if:

  • Cold engine at idle running stably without jerking
  • A hot engine gives out understated revolutions in idle mode
  • Sufficient headroom remains before the cutting system starts to work
  • Stable engine operation in any position

Note: From the FORTE factory, the lower screw H (idle), from a fully tightened state, was unscrewed by 8 revolutions and 2 hours (at this stage it should be). Recommended idle speed for FORTE engines is 2900 rpm.

Left screw L. Fine adjustment of the highest idle speed.

Important! The engine of FORTE petrol lawn mowers should not run at maximum speed for more than 10 seconds.

Open the throttle, start the engine and lightly turn the screw clockwise until the engine speed decreases.

Then slowly turn the screw L in the opposite direction until the engine starts to shake.

Finally, turn the screw clockwise a short distance again until the mower engine starts to operate in the appropriate mode for itself.

Do-it-yourself lawn mowers carburetor adjustment

Lawn mowers, like all gas powered garden tools, are not difficult to maintain. It is possible and necessary to repair, configure yourself. For example, adjusting the carburetor of a lawn mower with your own hands is a matter of five minutes.

A lawn mower carburetor is a unit in the power system. In it, like any carburetor, there is a process of mixing air and fuel (gasoline) for further supply to the engine cylinders.

Lawn mowers carburetor device

The base of the carburetor is an aluminum body. It contains a diffuser (hole with internal contours). Air is blown through this hole. The flow rate of oxygen (air) depends on the cross-section (orifice) of the diffuser.

The diffuser is equipped with fuel channels. Fuel is drawn in from them using an air stream.

Outside the carburetor is installed:

  • Fuel pump;
  • Jet system;
  • Fuel-air mixture control system;

The main problems and malfunctions of the carburetor.

Mesh filter. There are often only two problems with this element:

  1. Blockage.
  2. Breaking.

In order to find out the cause of the breakdown, the fuel filter cap is unscrewed to remove the strainer. If dirt just accumulates on it, then flushing in gasoline or blowing will help.

If there is visible damage to the mesh filter, it is imperative to install a new one. There may also be damage to the fuel supply pipe (during repair, they practice checking this element).

The carburetor starter in most cases does not function due to blockages. Use acetone or the same gasoline for flushing.

Blowing compressed air into carburetor parts is an acceptable and convenient repair practice.