The Stihl 180 chainsaw (aka Stihl MS 180) is the most popular and recognizable model of the German brand. This chainsaw is simple and reliable. The only unit that requires close attention is a carburetor. This article will discuss the carburetor adjustment, its repair and maintenance.
What carburetor is used on a Stihl 180 chainsaw
The Stihl 180 chainsaw has a Japanese Zama carburetor of membrane type. Some users are confused by the inscription China on the carburetor. Yes, indeed they are going to China. But the plant is owned by Stihl (Stihl), and quality is still high. However, the chainsaw also has Chinese counterparts with corresponding carburetors. But such saws are usually cheaper than the original.
How the Stihl 180 carburetor works: device, principle of operation
The main components of the Stihl 180 chainsaw carburetor are the following components:
- fuel pump (with internal diaphragm);
- main (membrane) chamber;
- throttle and air flaps;
- needle valve;
- fuel jets;
- nozzle with valve;
- idle speed screw.
The principle of operation is as follows. The chainsaw crankcase is connected to the fuel pump in the carburetor by a special channel. Due to the alternating stroke of the piston, a vacuum is created in the engine crankcase. As a result, the diaphragm rises in the fuel pump and the valve for supplying fuel to the carburetor opens.
Further, the fuel passes through a filter element (mesh) and through a special channel enters the main chamber. A control membrane is installed in this chamber, which regulates the fuel supply by pressing the rocker arm, which in turn lowers the needle valve.
For raising the control membrane is responsible for the vacuum that occurs in the carburetor diffuser due to the rotation of the air, throttle valves. Once the engine has started, the mixture needs to be leaner. We lower the air damper, the vacuum in the diffuser is minimal, the membrane falls into place.
From the main chamber, fuel enters the diffuser using a nozzle with a check valve, or through idle jets (when the gas throttle is closed). There it mixes with the intake air and the finished mixture enters the engine cylinder. The non-return valve prevents air from the diffuser from entering the main chamber.
Carburetor Adjustment Stihl 180 Chainsaw
Usually, special screws are responsible for the quantity and quality of fuel entering the diffuser, by adjusting which we change the cross section of the fuel channel. But on the used carburetor of the Stihl 180 chainsaw, to facilitate the operation of the saw, these two screws are missing.
The channels are designed so that the optimum amount of fuel gets into the diffuser at all engine speeds. And for the adjustment here, the LD screw is responsible, the rotation of which regulates the air supply to the idle jet. Due to which there is a change in engine speed.
So, to adjust the carburetor of the Stihl 180 chainsaw, you will need an ordinary flat screwdriver and an electronic tachometer (not necessary). The adjustment algorithm is as follows:
- Check air filter. If necessary, replace the filter element.
- Screw the LD screw counterclockwise to the end, and then unscrew by 2 turns. Attention, the left thread! A hole for a screwdriver is provided for access to the screw on the saw body. Start the engine and warm up for 5-7 minutes.
- Turning the LD screw slowly clockwise, arbitrarily adjust the idle speed. There are 2 possible situations:
- The engine idle speed is very small. The engine does not keep idle. Turn the LD screw until the saw starts to rotate, and then turn the screw 1/2 back (the chain should stop).
- The saw spins idling. In this case, slowly turn the screw counterclockwise until the chain stops, then turn the screw another 1/2 turn in the same direction.
If after all the manipulations with the carburetor settings, the chain continues to spin at idle, you need to give the saw to the dealer at the service center.
The video below provides a detailed adjustment of the carburetor of the Stihl 180 chainsaw using an electronic tachometer.
Carburetor Repair Stihl 180 Chainsaw
The main malfunctions of the carburetor of the Stihl 180 chainsaw include the following.
- Gas does not enter the carburetor. The commonplace reason is a fuel pump failure. The diaphragm has lost elasticity or has lost weight. This happens due to material fatigue during prolonged use. As a result, with a vacuum in the engine, the diaphragm does not rise and does not open the fuel channel with the valve. It can be replaced by a spare from the repair kit by dismantling the carburetor.
- Gasoline may also not flow due to a clogged filter element (mesh) in the channel between the fuel pump and the needle valve. It is also treated with a replacement from the repair kit.
- Carburetor overflows. It’s not hard to guess that the problem lies in the main camera. Dirt particles enter the cavity between the needle and the channel, i.e. the valve does not completely close the channel when necessary and fills the chamber. Very often, the membrane ceases to fulfill its functions due to stretching (natural wear). As a result, when lowering, the membrane does not fully raise the needle, and fuel continues to flow. The main membrane is also part of the repair kit. Replace it is not difficult.
- Very often, after winter downtime, owners of Stihl 180 chainsaws face a difficult start. In this case, the valve sticks in the nozzle. The manufacturer recommends that you burn the remaining gasoline in the carburetor before putting the chainsaw in storage. Gasoline is prone to evaporation and during long-term storage, engine oil remains in the carburetor, upon contact with which the nozzle valve begins to stick to the body. As a result, fuel does not enter the diffuser. Since the nozzle is not part of the repair kit, you have to knock it out and rinse thoroughly. This must be done very carefully.
- If an idle nozzle or nozzle is clogged, it is enough to blow them with compressed air. Or rinse with gasoline, in 90% of cases it helps. But you cannot use needles or wires, as there is a risk of changing the flow area, thereby changing the throughput of the nozzles.
Video: Stihl 180 Idle Adjustment
A common problem due to which the Stihl 180 is unstable is the loss of the retaining ring on the axis of the throttle, as a result, it begins to dangle and play, which in turn leads to interruptions in work.
So, you decided to remove the carburetor and carry out diagnostics. The removal procedure is as follows:
- Pull the trigger and lower the choke lever down. We turn the latch and remove the chainsaw cover.
- We unscrew both fastening nuts with a socket wrench for 8 and remove the air filter with the housing.
- Remove the thrust of the gas (throttle) carburetor.
- Disconnect the cable from the control lever
- We take out the engine control lever from its place. At the same time, we disconnect the draft of the air damper.
- Pulling the carburetor towards you, remove it from the studs. Do not forget to disconnect the fuel supply hose.
A more detailed and intuitive algorithm for removing the carburetor from a chainsaw is presented in the video.
As for the disassembly of the carburetor chainsaw Stihl 180, then everything is simple. 1 bolt is unscrewed on the cover of the fuel pump and 4 bolts on the cover of the main chamber. This is enough to change all the necessary components from the repair kit.
After disassembling, the carburetor must be rinsed in gasoline, and the channels and jets must be blown with compressed air. In no case should you blow out the carburetor under high pressure and in the assembled state. Otherwise, you may stretch the membrane or diaphragm. The carburetor will stop working properly.
In order to assess the state of the filter mesh and membrane, you need to perform the following sequence of actions:
- Unscrew the screw.
- We evaluate the condition of the membranes, remove dust and dirt, if necessary, change the membrane to a new one. Everything should be clean under the membrane There should be no dirt on the membrane.
As for the Stihl 180 carburetor repair kit, it includes a set of gaskets for covers, a diaphragm and a membrane, a needle valve, a rocker with an axle and a spring. The price of such a kit is from 100 to 400 rubles.
Advantages and disadvantages
Zama carburetors are very reliable and easy to operate. Specifically, a carburetor is installed on the Stihl 180 chainsaw, on which there are no screws to adjust the quality and quantity of the mixture, as we are used to. One screw greatly simplifies the adjustment.
The membrane carburetor has no significant drawbacks. With such a carburetor, the chainsaw works in any position. With side cut, vertical, etc.
Despite the above advantages, the carburetor is sensitive to fuel quality. In addition to clean air from the air filter, it is required to supply purified fuel from the gas tank to the carburetor. But this is not always possible, therefore, at least once every six months it must be cleaned and purged.
How much is a new carburetor
Stihl 180 chainsaws are in great demand, primarily due to their reliability. The carburetor was no exception and also quite reliable and unpretentious. Adjustment or repair of the carburetor is required only after prolonged use, at least 5-7 years later (with an average load). The setup process itself is maximally simplified by Stihl engineers, this is the first chainsaw in which only one screw is provided for adjustment.