Owners of a popular model Stihl MS 180 Often faced with a situation where the tool stops starting or stalls immediately after launch. The most alarming symptom in this case is the leakage of gasoline from the air filter or the appearance of black “fat” candles. This is a sure sign that carburetor fuel, disrupting the correct proportion of the mixture.
Ignoring this problem can lead to a hydraulic shock in the cylinder, which is fraught with serious damage to the piston group. Understanding the principle of operation of the node and knowledge of typical malfunctions allow you to eliminate the defect with your own hands without contacting the service center. In this article, we will discuss the mechanics of the process in detail and point out the specific details that require attention.
The main reason lies in the violation of tightness or improper operation of the shut-off needle. When the fuel does not overlap in time, the chamber is overflowing and the gasoline begins to flow into the cylinder in excess quantities. This not only makes it difficult to start, but also flushes the lubricant from the cylinder walls, increasing engine wear.
The operating principle of the fuel system Stihl MS 180
Chainsaw carburetor Style 180 works on the membrane principle, where the fuel supply depends on the vacuum created in the crank chamber of the engine. The key element here is stop-needlewhich is driven by a rod bound to the membrane. When the fuel level in the chamber drops, the membrane lowers and opens the needle, triggering the gasoline.
If this mechanism fails, the fuel mixture becomes re-enriched. In normal condition, the mixture of air and gasoline has a strictly defined proportion, which ensures stable combustion. Disruption of balance leads to the fact that the spark plug “throws”, and the spark cannot ignite the wet electrode.
⚠️ Attention: Attempts to start a flooded chainsaw "from the pusher" or frequent jiggling of the starter can lead to breakage of the ratchet or break of the starter cable.
The system also includes a pump section that supplies fuel from the tank. Any disruption to the valves or damage to the pump membrane can cause excessive pressure, which pushes fuel through the shut-off valve faster than it has time to burn.
Before starting any work with the carburetor, be sure to close the fuel crane (if any) or pinch the fuel hose to avoid additional spillage of gasoline.
The main causes of fuel overflow
There are several key factors leading to the described problem. Most often, the culprit is wear or pollution of moving parts. Let’s look at the most likely scenarios that require the intervention of a master.
The first and most common reason is the loss of tightness of the needle or the presence of debris under its saddle. Even a microscopic villi or grain of sand does not allow the needle to tightly close the feed channel. As a result, gasoline flows in a continuous stream, ignoring the position of the membrane.
The second important aspect is the state of the membrane itself. Over time, the material tans, cracks or deforms. If the membrane has lost elasticity, it cannot react in a timely manner to the pressure change and open/close the needle at the desired speed. This leads to a chaotic supply of fuel.
- 🔹 Wear or deformation of the valve stop needle and seat.
- 🔹 Getting garbage, shavings or water into the fuel chamber of the carburetor.
- 🔹 Fossilization or loss of elasticity of the pump membrane.
- 🔹 Incorrect adjustment of the screws of quality and quantity of mixture.
It is also worth mentioning the possible damage to the snail. This lever connects the membrane to the needle. If it is bent or has a backlash, the force from the membrane is transmitted incorrectly and the valve does not close until the end. Visual inspection of this detail often reveals hidden defects.
Diagnosis of needle and membrane malfunctions
To accurately determine the cause, it is necessary to dismantle the carburetor and carry out a defect. You should start with a visual inspection of the float chamber. The presence of sludge, rust or water immediately indicates the need to clean the entire fuel system, including the tank and filters.
Pay special attention valve-needle. There should be no production, scratches or soot on its cone. In the model MS 180 A plastic needle is often used, which wears off over time. If the tip of the needle became flat or furrows appeared on it, sealed overlapping of the channel will never happen.
The membrane is checked by assessing its rigidity and integrity. Press the center of the membrane with your finger: it should be easy to bend and return to the original position. If the material has become rigid, like cardboard, or cracks appear when bending - the part is subject to mandatory replacement.
How to check the tightness of the needle without disassembly?
Remove the carburetor, flip it up with the inlet hole and feed fuel through the hose. If gasoline drips from the diffuser with a closed needle - the tightness is broken.
Do not forget to check the condition of the gaskets under the carburetor. Suction of air through damaged gaskets can knock down the membrane, creating a false overflow sensation, although in fact the vacuum in the crank chamber is disturbed.
Table of signs and methods of elimination
Data systematization helps to make a decision on repair faster. Below is a table linking symptoms to probable causes and methods of their elimination.
| Symptoms. | Probable cause | Elimination method |
|---|---|---|
| Gasoline pours out of the filter | Does not hold a needle or torn membrane | Replacement of the carburettor remake |
| Black candle, silencer smoke | Re-enriched mixture | Adjustment of screws H and L, cleaning of jelly |
| Saw's dead on singles. | Canal clogging or air suction | Purging the carburetor, replacing the gaskets |
| Difficult launch "to hot" | Overflow at stoppage time | Checking the stop-needle for wear |
| Floating speed | Unstable fuel supply | Defection of the membrane and the beef |
Using this table allows you to cut off unnecessary options and focus on the main thing. For example, if the candle is dry but the gasoline is pouring, the problem is clearly in the ignition or compression system, not in the overflow of the carburetor.
The process of adjusting and adjusting the carburetor
After replacing worn parts or cleaning the carburetor must be properly configured. On the hull. Stihl 180 Usually there are two adjustment screws: L (low speed) and H (high turnovers). Sometimes there's a third screw. LA or Tidle control.
The basic setting is made on a warmed-up engine. First, the screw. L achieve maximum speeds at idling, then the throttle reset them to stable operation. Vint H It is responsible for power and must be configured so that the saw gains momentum without failures.
☑️ Algorithm of setting the carburetor
If you are high in the mountains, the mixture may require correction towards depletion. However, under normal conditions, factory settings are optimal.
⚠️ Warning: Never leave the chainsaw to work at maximum speeds without loading for a long time - this can lead to overheating and bullying of the piston group.
Prevention and care of the fuel system
To the problem of overflow does not return, it is necessary to observe the rules of operation. The quality of the fuel mix plays a crucial role. Use only fresh gasoline with an octane number not lower than AI-92 and high-quality two-stroke oil in the proportion specified in the instructions (usually 1:50 for the first time). Stilet).
Old fuel is oxidized and forms resinous deposits that clog the jelly and stick the needle. If the saw is not planned to use for more than a month, gasoline from the tank and carburetor is better to fully develop or drain.
Regular replacement of the fuel filter in the tank will also prolong the life of the carburetor. Dirty filter creates additional thinning, which the pump membrane may not compensate, which will lead to work on a poor mixture and subsequent overheating, or, conversely, to a violation of tightness.
Replacing the fuel filter and using fresh mixtures prevents 80% of carburettor problems.
Frequent mistakes in repairs with your own hands
Many users, trying to save money, make mistakes that cost more than professional repair. The most common of these is the use of acetone or aggressive chemicals to clean plastic and rubber parts. This leads to instant destruction of membranes and seals.
Another mistake is ignoring the air filter. If the filter is clogged with dust, less air enters the carburetor, and the mixture automatically becomes richer. The user starts spinning the screws thinking the fuel is the problem, although it is enough to clean the filter.
The use of force in assembly is also dangerous. carburetor MS 180 It has plastic elements that easily crack when the screws are pulled. Use a dynamometer screwdriver or act with extreme caution when tightening the screws cross-cross.
Can I wash the carburetor without disassembling?
Partly yes, using special carburetor aerosols through the air filter hole. However, this will not remove the hard deposits inside the float chamber and will not restore the worn needle. Full disassembly and ultrasonic cleaning is more effective.
Why does the carburetor not start after replacing the saw?
Probably broken assembly sequence, forgotten gaskets, air sucker, or knocked down the basic adjustment of the screws. Also check if the model of the new carburetor matches the modification of your saw.
How often should the carburetor remake be changed?
With active use and high-quality fuel - once in 2-3 seasons. If problems with starting or overflowing are noticed, the replacement should be made immediately, without waiting for the planned maintenance.
Does the brand of gasoline affect the overflow?
Yes, low-quality impurities pollute the system faster. Also, the ethanol contained in some fuels can aggressively affect the rubber parts of old carburetors, causing them to swell.