Idle Trimmer Adjustment

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 a carburetor needs to be adjusted.

Idle Trimmer Adjustment

Principle of operation

A 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 mixes.

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 hole for the gasoline supply is formed, the tube has a narrowing. a 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. Setting up the carburetor for 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 find out 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:

  • It starts, but the engine immediately stalls. since the engine can only work when a certain amount of gasoline is supplied, if the fuel is too “lean”, that is, the supply channel is blocked, 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.

DIY lawn mowers carburetor adjustment

Setting up the module does not apply to repair and replacement of spare parts is not required. In this case, the lawn mowers carburetor repair kit will not be needed.

Three screws are provided for debugging:

  • L. is regulated first, since it is responsible for supplying fuel at low speeds;
  • H. he is responsible for the supply of gasoline at high speeds, as well as for fuel consumption and temperature;
  • T. it is used to debug idle.
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There are options, as a rule, this is the carburetor of a Chinese lawn mower, when only one screw remains on the body for debugging. for adjusting the idle speed. This does not mean that the module is configured automatically. it means that it will be difficult to carry out even such a type of repair as debugging. In the photo. adjusting the carburetor of a Chinese lawn mower.

  • The module is configured only when the engine is warm: for this, the device is pre-switched on for 10 minutes. If the mowing head rotates at idle speed, the debugging is started immediately: turn the screw T counterclockwise until the rotation stops.
  • Adjustment begins with screw L. The screw is turned to the right and left until it finds such a position at which idle speed does not become maximum.
  • Then the screw is turned 1/4 turn counterclockwise. This will be his working position.
  • Idling must be adjusted by turning counterclockwise to increase the number of revolutions and clockwise to decrease it. Its debugging consists in achieving such a mode in which a sufficient number of revolutions are made before the start of rotation of the mowing head. In this case, the engine must work stably at different positions.
  • The position of screw L is determined last. at maximum speed, the trimmer should not work for more than 10 seconds. The throttle opens, the screw turns clockwise, very slowly, until a decrease in the number of revolutions is audible.
  • Then, also slowly, the screw rotates counterclockwise until the motor begins to malfunction. Then the screw is turned back clockwise until the engine starts working normally again.

If there is a tanometer, and if the recommended rpm values ​​are indicated in the product passport, the correction can be made more accurate, focusing not on hearing, but on the readings of the device.

Carburetor adjustment of lawn mowers is not carried out by ear.

7 comments on the entry "Adjustment and repair of the carburetor lawn mowers"

    Dmitry Pavlovich 07/04/2016

Please clarify. In the adjustment section, item 5, screw L. error? Should you read screw A? Thank you.

Prompt start position of screws H L LA


Prompt start position of screws H L LA

Thank you very much for the accelerator and did not know, but the defect is very important and creates a huge problem that almost everyone is silent about. BRAVO….

Maybe all the same tachometer is a rpm meter, not a tonometer blood pressure meter

And I have L, H, LA, it’s LA instead of T?

The heart of any chainsaw is a two-stroke internal combustion engine.

The trimmer is not a complex household appliance, so most of its floor.

There was a need to purchase a reliable and reliable mechanical tool.

Gone are the days of Soviet agro-industrial gigantomania. Gig gone.

Tiller is an economical tractor option for small jobs.

In order to make such a nozzle as harrows, with your own hands, in addition to ph.

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? Primarily to make sure that the engine is working properly and that the maximum productivity of the tool is 100% ensured.

Setting the carburetor for FORTE lawn mowers:

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

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2. Gently rotate the right and left needles to the middle position. Important! Do not under any circumstances twist by the stopper. this can damage the engine).

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

  • Right H. low speed screw
  • Lower T. idle screw
  • Left L. high speed screw

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

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 look at "11 o’clock".

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

Correct adjustment is only considered if:

  • Cold engine at idle running stably without jerking
  • A hot engine gives out understated rpm at idle
  • 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. 2900 rpm.

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

Important! The engine of FORTE petrol lawn mowers at maximum speed must not run 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 lawn mower engine starts to operate in the appropriate mode for itself.

Lawn mower Stihl FS38. Description of the model. Features of operation, maintenance. Stihl Fs 38 Trimmer Carburetor Adjustment

Annotation for adjusting the carburetor lawn mowers.

Signs of imbalance

Debugging the carburetor is certainly done during the manufacture of the apparatus. Lawn mower texas 330 carburetor adjustment. Usually, the owners will find out about the need to adjust the fuel supply with their own hands only after rather severe breakdowns, in the process of correcting which, the module was removed and, for example, cleaned.

Signs of a failure in the settings are the following:

  • It starts, but the engine stalls here. since the engine can only work when a certain amount of gasoline is supplied, with a very "poor" fuel, in other words, if the supply channel is blocked, the engine will stop;
  • Very high fuel consumption, a lot of exhaust gases. the result of incomplete combustion of the consistency. In this case, on the contrary, there is a lot of fuel and the mixture comes out extremely dense.

Specifications and features

  • Mowing width: 23 cm;
  • Fuel tank capacity: 0.33 l;
  • Weight: 4.1 kg;
  • Barbell: curved;
  • Line thickness: 2mm.

Thanks to the manual fuel pump, a person will easily be able to pump fuel into the carburetor. This point is especially important in a situation where the mower has been idle for a long time. Constantly adding fuel will allow you to quickly start the device even after a "long vacation".

Together with the unit, the owner receives protective goggles and a mowing head in the complete set. You can understand the assembly features and other specific points of operation thanks to the manual presented on our website.

For other useful information, see the following document:

The curved boom of the STIHL FS 38 lawn mower with a rounded handle is worthy of attention. Thanks to this design, the device easily copes with cleaning the area even in narrow or confined spaces.

All controls are located on a comfortable handle, so it takes a long time to look for where and what to switch is not necessary. During work, such a moment is very important, because the operator can not be distracted and without unnecessary movements adjust the operation of the machine.

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The Stihl FS38 lawn mower belongs to the light group and is the optimal complement to the powerful lawn mower for trimming hard-to-reach areas, along paths, under trees and bushes. With STIHL mobile lawn mowers, you can quickly cut soft overgrown grass on lawns and lawns, always keep a small area tidy.

Idle speed adjustment with screw LA (T).

The second stage of the adjustment is the correction of the idle speed with the LA (T) screw, here the installation is carried out exclusively by ear. Turning the screw clockwise, you increase the speed, turning it counterclockwise, you decrease the speed. It is important to ensure that the mower’s head does not spin when idling. It should also be noted that screws L and LA are adjusted in pairs, that is, changing the adjustments on one screw may require changing the adjustments on the second. After you have achieved smooth operation of the engine with a minimum of vibrations, go to adjustment H.

Trimmer adjusting screws.

Regardless of the trimmer manufacturer, each trim has three adjusting screws (very rarely two) that adjust the carburetor’s performance. Let’s take a look at the types of adjustments using the example of the professional hedgecutter Stihl fs 450.

Trimmer adjusting screws

This trimmer has three adjusting screws:

  • Top left screw (H). adjusts the amount of fuel supply at high rpm;
  • The upper right screw (L). adjusts the amount of fuel supply at low rpm (idle);
  • Bottom left screw (LA). corrects the amount of idle, this screw can also be designated with the letter T;

Adjusting the amount of fuel delivery at low speeds L.

First of all, the upper right screw L is adjusted, that is, the amount of fuel supply at low speeds is adjusted. For Stihl fs series trimmers, screw L is turned clockwise all the way, then returned one full turn counterclockwise. This adjustment is relevant for many other trimmers. If we go from private to general, then you should achieve stable idle speed when turning the screw L, that is, the lawn mower should work smoothly and without unnecessary vibrations, as soon as you have done this go to the screw LA (T). It should also be noted that by turning the screw counterclockwise, you add fuel to the mixture, while rotating it clockwise, you reduce the amount of fuel in the mixture;

DIY trimmer adjustment.

Adjusting the carburetor trimmer.

Adjustment of the trimmer (lawn mowers) should be done in accordance with the technical data sheet. It would be most correct to read the information in the instructions for your trimmer. It usually details how to adjust the lawn mower. If you do not have instructions for the trimmer, then you can use our advice.

Steps for adjusting the carburetor for lawn mowers:

  • Correction of the amount of fuel supply at low rpm L;
  • Correction of idle speed with screw LA (T);
  • High RPM Fuel Trim. H.

High RPM Fuel Trim. H.

The third stage, correction of the amount of fuel supply at high rpm. H. For Stihl trimmers, unscrew the screw counterclockwise until it stops, then turn it a quarter clockwise. In general, trim adjustments from other manufacturers are almost the same. The screw is unscrewed completely counterclockwise, then the lawn mower starts and full throttle is squeezed out. Then turning the screw clockwise (usually 1/4, 2/4 turn) will decrease the maximum speed by about 5-10%. This completes the lawn mower adjustment. When adjusting the carburetor with this screw, turning clockwise, you reduce the fuel supply, while turning it counterclockwise, you increase.

Adjusting the H trimmer