Complete Stihl Disassembly 180 Videos
A chainsaw is needed in construction, in horticulture, and in landscaping. its presence greatly simplifies the implementation of a number of wood processing tasks. The main unit of this tool is an engine, the operation of which largely depends on the condition and settings of the carburetor. It is here that the fuel mixture is prepared. So, if the saw does not start, stalls or does not provide the required power, it is likely that the reason for this is the incorrect operation of the carburetor. Fortunately, in many cases you can deal with this yourself. Only for this you need to know and understand the device and the principle of operation of this unit and, of course, the chainsaw itself.
How is a chainsaw carburetor designed?
The main purpose of the carburetor is to mix fuel with air in the required proportions. If the latter are violated, this almost immediately affects the engine.
Chainsaw carburetor Stihl MS 181 C BE
Chainsaw carburetors may differ in design. However, their basic elements and the principle of operation remain approximately the same.
- The foundation
This is a wind tunnel, across which there is an air damper. with its help, the air supply intensity is regulated.
This part is where the base tube is contracted. here the air flow rate rises, i.e. air always flows into the carburetor under some pressure.
In this area, fuel is in contact with the air stream. Fuel enters the atomizer from the float chamber through the nozzle (dispenser).
- Float chamber
This is a container that allows you to keep the fuel mixture in a stable state.
The design of the carburetor chainsaw
A chainsaw carburetor works according to the following principle:
- when the engine starts, the main damper opens and an air stream is supplied into the air duct at a certain speed;
- the air flow rate, as well as the level of the float in the chamber are regulated by the position of the damper, namely due to the pressure difference in the float chamber and the air channel;
- fuel from the float chamber is sucked into the nozzle, and from there into the diffuser;
- passing through the diffuser, air captures the incoming fuel;
- the resulting mixture is fed into the cavity of the cylinders through the inlet channels.
The principle of operation of the carburetor chainsaw
The pressure in the float chamber is approximately equal to atmospheric, but in the air channels of the carburetor when the engine starts the chainsaw, a vacuum occurs. Opening the damper increases the air supply. As a result, more fuel enters the carburetor, and the number of revolutions of the engine shaft increases.
What is the primary adjustment for?
In the first hours of operation, the 2-stroke engine of the chainsaw requires a break-in, on which the quality of its further work depends. During the break-in process, the carburetor is initially adjusted. the optimal parameters for preparing and supplying the fuel mixture are established.
Primary break-in of the chainsaw: work with thin material
Most modern chainsaws go on sale regulated. Nevertheless, the quality of the factory settings does not stop to check. in the end, it is up to you to work with the tool.
At the first start, the chainsaw should work in a gentle mode. Therefore, for several hours after the start, it is recommended not to overload the engine and cut only small branches and trunks up to 10 cm thick.
Simple rules will help to insure against failures in the operation of the carburetor of the chainsaw:
- Always mix gasoline and oil according to the figures given by the manufacturer.
The proportions of the fuel mixture for the chainsaw engine
A chainsaw should start correctly, provide a stable sprocket rotation speed and a smooth increase / decrease in power. When the engine is running, there should be no extraneous knocks, pops or noises.
Professional hand chainsaw at work
The main thing during the initial run-in of the tool is to ensure that the fuel consumption matches the power used, i.e. in practice, the saw should not go out, “sneeze”, smoke and jerk.
How to recognize faults in the carburetor?
Typical carburetor malfunctions are easy to recognize. They are expressed in the fact that the engine of the chainsaw starts and stalls immediately or does not show any signs of life at all. Well, or with might and main consumes fuel, instead of the intended power producing clouds of black smoke and aggressive vibrations.
Video: Complete Stihl Disassembly 180 Videos
Chainsaw carburetor operation scheme
Carburetor settings may be affected by:
- lack of fixation of adjusting screws;
Chainsaw adjustment screws
New Husqvarna 365 chainsaw chainsaw
Chainsaw Air Filter with Nylon Tab
Detected problems should be fixed immediately. But how to determine that it is in the carburetor? To do this, follow how your tool works.
A list of typical signs that carb settings have gone wrong include:
- Unstable motor
Typically, the reason for this is the use of the wrong (lean) fuel mixture.
- Fuel overrun
It is expressed in increased emission of exhaust emissions, which acquire a black color. This means that fuel is not completely consumed, i.e. the mixture is oversaturated.
The carburetor is set correctly. the saw starts up the first time
- Arbitrary changes in engine power
May be due to damage to the fastening screws or protective cap.
- Increased fuel consumption, accompanied by vibrations and claps
It speaks of the critical wear of the piston group, so adjusting the carburetor will postpone the overhaul only for a while.
- Sneezing and jerking engine
This picture is observed when the carburetor channels are clogged or its filters malfunction. In this case, adjustment should be carried out only after thorough washing of the unit.
Chainsaw Fuel Filter
Despite the fact that the carburetor is the most difficult part of the engine, you should not get upset when it detects a malfunction. Instead, you need to arm yourself with some kind of tool, a constructive knot diagram, and healthy logic.
Chainsaw carburetor in repair
DIY disassembly: nothing complicated
First of all, you need to prepare a place for disassembly. It can be a workbench or a regular table. In addition, you need a rectangular piece of cloth or cardboard. on it you will carefully fold the details of the carburetor. And finally, the tool: to disassemble you will need a set of open-end wrenches and screwdrivers, a special cleaning compound and an ultrasonic cavitation bath.
Chainsaw Carburetor Repair Tool
First, you have to dismantle the carburetor of the chainsaw. This is done in this order:
- To get to the carburetor, you need to remove the top cover of the chainsaw, fixed with three bolts.
Carburetor Cover Removal
Removing the fuel hose and drive rod
Throttle Cable Removal
After removing the gas hose, the carburetor is ready for disassembly
Dismantling the carburetor must be performed in the manner prescribed by the design and functional solutions of its elements. The carburetor parts of the chainsaw do not differ in size, so you need to fold them carefully and in order, trying not to lose anything.
Dismantling the chainsaw carburetor in the photo
After disassembling, it is necessary to carry out troubleshooting and replace damaged or worn parts. Next, the entire kit should be washed with a special tool, dried and wiped with a dry, lint-free cloth. The nozzles and tubes of the assembly must be purged with compressed air, or, in order to more thoroughly remove the formations on their internal surfaces, before that they will be treated with ultrasound.
Carb Adjustment: Highlights
Reassembling the carburetor is carried out only after complete cleaning, drying and blowing with compressed air. At the same time, do not forget that some gaskets and seals must be replaced even if there is no damage.
You can start adjusting the carburetor provided that it is correctly diagnosed, assembled properly and flawlessly mounted on the engine again.
Carburetor tuning principles:
- the H and L screws adjust the ratio of air to the combustible mixture, i.e. throttle position. Tightening the screws clockwise leads to lean mixture and the motor goes to low revs. When unscrewing (counterclockwise), the mixture is enriched, and engine speed rises;
- screw T is responsible for adjusting idle speed: turning it clockwise gives an increase in their number, against. a decrease;
- the screws are adjusted in L-H-T order.
Chainsaw Carb Calibration
The general adjustment algorithm looks something like this:
- Initially, the highest idle speed is found by turning the screw L and then returning it to ¼ turn counterclockwise. If the chain is idling, turn screw T in the same direction until it stops completely.
- When the engine is running at full speed, turn screw N by ¼ turn to the left, and then let the engine run for 10 seconds to check the maximum speed indicator using a tachometer. It must correspond to the number indicated in the instrument passport.
- After calibration with screws L and H, screw I is used to adjust idle speed. If everything is done correctly, the engine will work evenly in all its positions.
Instructions for calibrating the carburetor on the chainsaw body
Upon completion of the adjustment, it remains to reinstall the chainsaw cover with an insulating gasket, after which you can begin the main work. If the settings are correct, the engine of the chainsaw will receive the optimal fuel mixture. This will ensure its normal efficiency, as well as overall comfort and safety of working with the tool.