How to set up a carburetor on a chainsaw?
Carburetor adjustment consists in adjusting the jet and air damper so as to obtain the optimal ratio of the amount of air and fuel in the fuel mixture.
If there is a lot of air in the fuel mixture and there is a lack of fuel, the mixture is lean, therefore the engine power is reduced.
If there is a lot of fuel and a lack of air. the mixture is oversaturated, incomplete combustion of the fuel occurs, which leads to smoke, soot on the piston and in the exhaust pipe and increased fuel consumption.
The structure and principle of operation of the Husqvarna carburetor
To successfully tune your Husqvarna chainsaw carburetor, you need to know how it works and how it works. In fact, everything is not as difficult as it seems at first glance.
The saw carburetor has a built-in fuel pump, which is responsible for transporting a mixture of gasoline and oil, as well as a diaphragm, a needle valve with a rocker arm. Their joint work allows metering the fuel supply to the main chamber and two dampers.
One of the valves is designed to adjust the fuel supply to the cylinder when the gas is pressed, it is called the throttle, the second is responsible for limiting the air supply from the air filter to facilitate starting a cold Husqvarna chainsaw. At the moment when the operator cuts off the air supply to the carburetor with the help of the air damper, the fuel mixture becomes leaner and its supply to the cylinder increases, due to which the chainsaw starts much easier than when a cold start is carried out in normal mode.
In the operation of the Husqvarna carburetor, a nozzle valve is involved, which atomizes the fuel and prevents air from entering the main chamber. Often, problems with the operation of the saw can be caused by defects in this particular element. For example, a valve, if the chainsaw is not stored properly, may stick, the fuel supply will stop, which will make the engine impossible to operate. Also, irregularities in the operation of the injector can cause air to leak into the main fuel chamber of the carburetor. In such cases, adjusting the position of the adjusting screws will not correct the situation, it will be necessary to repair or replace the unit.
Three adjusting screws installed in the carburetor body are responsible for setting the quality and quantity of the mixture, as well as the number of revolutions of the crankshaft in idle mode:
Chainsaw stalls when pressing on gas. How to adjust the carburetor
- screw (L). adjusts the amount of fuel in the low and medium speed mode;
- (H). is responsible for traction at high speeds and their number;
- (T). changes the position of the throttle valve, thereby regulating the amount of fuel mixture entering the cylinder and the operation of the engine of the tool in idle mode.
Screws (L) and (H) cannot be adjusted without specific knowledge and experience. Improper adjustment of the quality and quantity of the fuel mixture can cause the engine to stop working or malfunction, leading to rapid wear or even seizure.
Adjusting the carburetor of a Chinese chainsaw with your own hands
Adjustment is not provided for all carburetors of Chinese chainsaws. Today there are many models of household-grade chainsaws, including European brands, on whose carburetors there are simply no adjusting screws. Or there is only one idle speed adjustment screw.
Such carburetors require adjustment only when the chainsaw at idle speed makes too few exhausts (rpm) and sometimes stalls. Below in the text, the algorithm for adjusting the idle speed of the carburetor on a Chinese chainsaw will be considered.
How to properly adjust the carburetor?
Consider, as an example, adjusting the carburetor of a Partner chainsaw.
To adjust, you need to have a slotted screwdriver and a device. a tachometer, which allows you to measure the engine speed.
The setting is carried out in the following sequence:
- tuning the carburetor of the chainsaw at low speeds;
- adjustment at maximum speed;
- fine tuning to work at idle speed;
- checking the operation of the saw in all modes.
You need to start after the engine has been running and warmed up.
The chainsaw is adjusted using three adjusting screws on its body:
- screw L. adjusting the fuel supply at medium and low speeds
- screw H. at high speeds;
- screw T. at idle.
If the carburetor is completely misaligned and the engine does not want to start, set the adjusting screws L and H to the standard setting: first tighten them completely, then unscrew them half a turn.
Start the engine and let it warm up, then start adjusting low rpm with screws L and T.
To do this, screw L should be unscrewed until the maximum engine speed is reached, and then screwed in ¼ turn, and set the idle speed with screw T.
Further, to adjust to maximum speed, slowly tighten the screw H, achieving maximum speed according to the tachometer.
After completing the adjustment, it is important to check the operation of the engine in all modes. To do this, you need to drown it out and let it cool
Then start the saw in cold start mode and observe the engine idling. If the gas gradually increases and decreases, and the chain does not move, the adjustment is correct. The next step is to check while cutting. If there is a loss of power, re-adjust.
DIY carburetor repair
The carburetor is easy to disassemble, so you can repair the chainsaw carburetor yourself. For example, if necessary, it is quite possible to do the following operations with your own hands:
- replace the gasket under the cover of the main chamber;
- flush or replace the fuel filter;
- replace needle valve and fuel pump diaphragm.
Before proceeding with the disassembly of the carburetor, it is necessary to clean the dirt from the surface of the body, as it can get inside the carburetor and clog the holes of the needle valves and the jet.
Next, you should undock the fasteners of the air and throttle control rods, dismantle the air filter and remove the cover of the main chamber by unscrewing the fastening screws. After that, you can start replacing the mentioned parts.
Very often, the reason for not starting the saw can be defects in the ignition system, in particular, spark plugs due to the following reasons:
- carbon deposits on the candle. indicates poor quality oil or improper carburetor adjustment;
- filling the spark plug with fuel. incorrect carburetor adjustment.
To check the condition of the spark plug, unscrew it with a special wrench from the cylinder head.
The carbon deposits on the candle are removed with a needle or awl, and, if necessary, with a sandpaper, then we put it in place and try to start the engine.
We wipe the flooded candle with a rag, dry it, put it in place and try to start the saw.
How to adjust the carburetor of chainsaw
In some cases, the engine smokes and stalls at high revs. The reason may be clogging of the muffler with exhaust products, so you need to remove the muffler, wash the carbon deposits with gasoline, wipe it, dry it and put it back in place. While the muffler is not in place, the exhaust outlet should be covered with a rag to prevent dirt from entering.
The design and principle of operation of the chainsaw carburetor
for mixing in certain proportions of oxygen and fuel
The carburetor device, in general, is the same in all saws, with the exception of Chinese-made chainsaws. But, in principle, it will not be superfluous to look into the data sheet of the instrument and study the structure of the carburetor. Its main components are as follows:
- tube. an element responsible for the portioned air supply by opening or closing the damper;
- diffuser. an element located at the inlet through which fuel is supplied and is designed to accelerate the air flow;
- atomizer. a mechanism for injecting fuel into the air stream;
- float chamber. a cavity designed to maintain the combustible mixture at the same level. It is from it through the nozzle that the fuel enters the sprayer.
Algorithm of actions for setting
The carburetor of the chainsaw is tuned in two stages:
- basic stage (engine on);
- stage two. perform when the engine is warm.
Important ! Some setup steps need to be adjusted depending on the Makita chainsaw model. In order to do everything right, read the instructions
- Turn the screws for adjusting high and low speeds until they stop (turn clockwise).
- At the moment of meeting resistance, make one and a half turn back.
Screw marked T, move clockwise. Release it only when the engine starts to run stably. At the same time, keep in mind that the chain should not move at this stage.
What if the engine shuts off during idle tuning? In this case, it is important to quickly turn the screw until it stops (turn clockwise). If manipulation causes the chain to move, turn the adjusting screw slowly back to its original position.