How easy is it to chainsaw carb adjustments?

Chainsaw carb adjustments: the best user guide from 2022

Proper carburetor adjustment will allow the saw to produce maximum power, prolong engine life, reduce emissions, provide smoother idling, rev up quickly and provide long-term trouble-free operation.

Be sure to use the correct ratio of gasoline to oil recommended for your chainsaw. The following information describes the process of adjusting the carburetor on a professional saw.


When is it necessary to adjust the carburetor of a chainsaw?

Here is an index of the numerous typical issues in which chainsaw carburetor adjustment is necessary:

  • The motor begins, while the chainsaw stalls, or it cannot be started at all. The reason may exist similarly greatly air-fuel mixture chamber.
  • High fuel consumption. It can occur due to excessive saturation of the fuel mixture adjustment that enters the engine with fuel. For the engine to work well, the mixture must be of high quality.
  • Debris entering the carburetor. This can happen if the filter is damaged or low-quality fuel is used. You will need to completely disassemble the carburetor, flush it, and re-adjust it.
  • The engine does not idle well or does not develop full power.

Attention! If the engine is not running well due to a worn piston, carburetor tuning will not work. In addition, along with the setting, it is desirable to clean the carburetor of debris – this will increase the efficiency of the procedure.

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Chainsaw carburetor adjustment

Before adjusting the carburetor of your chainsaw, you need to make sure that your chainsaw has the following:

  • Clean air filter.
  • Fresh, properly mixed fuel.
  • Properly functioning spark plug.

A dirty air filter, bad fuel, or a dirty spark plug intention impact the performance of your chainsaw engine. To properly adjust the carburetor, all other parameters must be in the correct working condition. Now that you keep a pure air filter, and fresh fuel, you are ready to adjust your chainsaw’s carburetor.

  1. Step: Close the inferior and high-speed fuel adjustment. Using the special adjusting tool, completely close the low-speed fuel adjustment (marked with an L on the carburetor) and the high-speed fuel adjustment (marked with the letter H on the carburetor). This is accomplished by turning both jets clockwise until they stop.
  2. Step: Fan the lower and high-speed injectors for 1.5 turns. Using a special adjustment tool, spread the low-speed fuel adjustment (marked with an L on the carburetor) and the high-speed fuel adjustment (marked with an H on the carburetor) 1.5 turns from secure.
  3. Step: Begin the chainsaw and adjust the low-speed jet until the chain stops. Using a special adjustment tool, low-speed fuel adjustment (marked with an L on the carburetor) so that the chain stops turning, and the throttle remains sensitive.
  4. Step: Adjust the high-speed jet to reach the maximum RPM allowed. Using the special adjusting device, adjust the high-speed jet (marked H on the carburetor) so that the engine runs at the maximum allowable RPM, as shown in the proprietor manual. Never exceed the maximum RPM rating for your chainsaw. Doing so may damage the chainsaw motor.
  5. Step: Optional. If required, adjust the idle screw until the chain stops moving. In some circumstances, it stands required to adjust the idle screw (marked T on the cover of the chainsaw) until the chain stops turning. If the idle is set too high, the chain will resume moving on its own. If the idle speed is assigned to lower, the chainsaw will not idle and will arrest.

Chainsaw engines have three carburetor adjustment screws

You will need a special tool for adjusting the low and high speeds and a high-speed screw for the idle control.

  1. Idle Speed screw/Throttle – This is an adjustment that controls how much the throttle stays open when the throttle trigger is released. If this adjustment is set too low, the engine will stall when the throttle trigger is released.The throttle valve (butterfly) simply shuts off the combustible air/fuel supply and the engine stops. If this adjustment is set too high, a high idle speed will cause the centrifugal clutch to engage and the chain to spin. This is a dangerous condition and should be avoided. It also causes excessive clutch wear.
  2. The low-speed fuel trim (labeled L) is an adjustment that adjusts the amount of fuel in the combustible air-fuel mixture at idle. A setting that is set too rich will cause the engine to “oil” and stall at idle. Too lean a mixture will starve the engine and cause racing. The extremely lean adjustment will also cause the engine to stall.
  3. The high-speed fuel trim (labeled H) is a trim that adjusts the amount of fuel in the combustible air/fuel mixture at cutting speed. It would be wrong to say that this is the most important setting because all these settings must be precise for the saw to perform at its best, but it is this setting that determines how the saw performs when cutting.
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Too much adjustment will prevent the saw from reaching the RPM required to achieve maximum power. Throttle response can also be sluggish, and the engine will smoke and run poorly. A too lean mixture will allow the engine to reach an RPM level where bearing failure and cylinder seizure are likely. It will also lack power during cutting and will get very hot.

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Adjustment procedure carburetor

The following procedure must be followed to ensure proper carburetor adjustment.

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  • Check the air filter and clean it if necessary. Adjusting a carburetor with an air filter partially clogged is similar to adjusting a carburetor with a partially closed choke. If you adjust the saw with a dirty air-fuel mixture, the saw will run too lean after cleaning the filter.
  • Inspect the mute and exhaust port for carbon deposits. Carbon blocking the spark arrestor or exhaust port net can push the saw to operate as if the carburetor needs adjustment. Changing carburetor sets with the muffler turned off can push the saw to operate lean after the carbon has been removed.
  • If carburetor adjustment is required due to a new or remanufactured carburetor, it is best to start with a single-turn fuel trim adjustment. This is achieved by carefully screwing the adjusting screws into their sockets and then backing them out one turn each.
  • Check the fuel level. The tank must be more than half full. If the carburetor is adjusted when the fuel tank is almost empty, the carburetor may be adjusted too richly when the fuel tank is full.
  • Start the engine and warm it up. Start the engine and warm it up. If the saw is idling, allow it to operate for a rare minute. If it doesn’t idle without stopping, warm it up by repeatedly depressing the throttle, don’t open the throttle all the way. Carburetor adjustments made on a cold engine will be to adjustment, slightly rich when it reaches normal operating temperature.
  • Start by setting the idle speed. Try setting the speed around 2700 rpm. If you don’t have a tachometer, try setting your speed so that the saw is idling as quickly as feasible without committing the clutch. Never put the idle so that the circuit will run when the throttle is released. If the saw does not idle, continue to the next step.
  • Set the low-speed fuel trim. Slowly turn the propeller in until the engine runs out of fuel. Note the position of the screwdriver slot. Now slowly back out the adjusting screw and the engine should run better.Continue turning the screw until the motor begins to load. Write down the position of the screwdriver slot and compare it with the position of the tilt adjustment. Now slowly turn the screw to the position where it works best at idle. It should be somewhere in the middle between rich and lean settings.
  • Click on the link below and the WAV sound clip will be downloaded to your browser. What you will hear is the idle speed of the saw. Slowly tilt the idle speed control, turning it until the idle speed rises, and then it starts to stall. Then we get richer and hear the saw begin to growl and the revs drop almost to the point of stalling.The optimal setting is between these two extremes. If you adjust too lean, it will run out of gas and die on acceleration. (Note that a saw set to slant at it can also stall on acceleration.) If you believe you’ve discovered the proper place, step on the gas, and the saw should accelerate up without any delay or struggle.

You may also be interested in: What is Rip Capacity on a Table Saw?


Frequently Asked Questions

What is the H and L on a carburetor?

Start by locating the three adjustment screws. They are typically labeled L (low-speed jet), H (high-speed jet), and I (idler jet).

What do the two screws on the carb adjust?

There should be two screws on the front of the carburetor, which are used to adjust the air and fuel mixture. Often these look like flat-head screws, and you can use a screwdriver to turn them, adjusting the amount of fuel and air mixing in the carb.

What does a carb adjustment do?

The primary goal of making these adjustments is to achieve the appropriate engine speed at idle while ensuring it runs as smoothly as possible. In doing so, you’re establishing the proper fuel and air mixture at idle and setting an excellent baseline for further tuning.

How do you adjust the idle speed on a chainsaw?

Turn the idle speed screw adjustment clockwise with a flathead screwdriver until your engine chokes off at idle. This stage alters how well your chainsaw idles in certain situations. Adjusting this setting eliminates popping and stalling caused by changes in weather or gasoline type.


The previous information briefly explains rich and lean conditions. It also lists the three adjustment screws and their purpose. It should be noted that on modern professional saws, most of these adjustments have “limiters” that determine the degree of adjustment of the carburetor.

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In most cases, the correct adjustment is in this range, but not always. If the correct adjustment of your saw is out of the narrow scope, bring the saw to the store. Occasionally, it’s driven by an issue with your saw, other times it’s just a matter of resetting the range on the stops.

Serg Cooper
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