How to change a piston on a Stihl 180 chainsaw
An article about the piston group of the Stihl MS 180 chainsaw. The main piston malfunctions and diagnostic options. Piston replacement algorithm.
When a piston needs to be replaced
There can be quite a few reasons why the piston needs to be replaced, as well as a completely piston one, but they can all be divided into natural ones and those arising from improper operation. Natural, this is the wear resulting from the long-term operation of the Stihl 180 chainsaw. There are much more artificial ones, for example:
- Overheating of the engine and the appearance of thermal seizures;
- Foreign body entering the cylinder and the appearance of mechanical scoring;
- Breakage of the piston ring as a result of exceeding the maximum engine speed;
- Breakage of the piston skirt due to overspeed;
- The use of low-quality fuel, as a result of which the piston group of the chainsaw wears out from the side of the intake channel in the cylinder;
- Operation of a Stihl chainsaw with a dirty fuel filter, as a result of which the percentage of oil in the fuel mixture is reduced;
It is necessary to diagnose the CPG if the Stihl ms 180 has suddenly lost power or does not start, while the starter of the tool does not turn. If the starter cranks, but the saw does not start, and there is a spark and the fuel enters the cylinder properly, it is necessary to measure the compression in the engine.
9.5 – 11 atm. It is considered a normal indicator at which the Stihl chainsaw starts up properly and delivers maximum power, if the compression is lower, there is a possibility that there are scuffs on the cylinder-piston group, or its wear is quite large. In any case, with reduced compression, for further diagnostics, it is necessary to completely disassemble the saw.
It is possible to determine the presence of scoring on the piston, as well as the breakage of the piston ring, if you remove the muffler and carry out a visual inspection of the visible part of the piston, while the rings can be checked for elasticity by pressing on them with a small screwdriver. There will be little movement on the working rings, a defective or jammed piston ring will not move.
On you can see the detailed instructions, in which the master showed in all details how to properly disassemble the saw and install a new piston on it. You can also see how the saw is cleaned correctly during the repair process.
Why the Stihl chainsaw won’t start after replacing the piston
If the saw does not start after replacing the piston, it is necessary to check the fuel supply to the chamber, as well as to diagnose the ignition system. Very often, when installing the control lever on the chainsaw, the craftsmen forget to connect the wires coming from the ignition coil, as a result of which the spark disappears and the saw does not start.
Also, the problem may lie in a pinched fuel supply hose or if it is not connected at all. Of course, there can be many reasons, but it is worth remembering that if all the work on replacing the piston is carried out correctly, the tool should start and work normally without any problems.
How to disassemble, repair and assemble a Stihl chainsaw
In order to repair the device, it must first be disassembled. You need to remove the side cover, saw chain and bar. Then clean the tool, blow it out with a compressor and brush all the components with a brush. Then remove the handle. To do this, remove the plugs from the shock absorbers with a screwdriver. After that, remove the shock absorbers and the handle.
Then the starter is removed. Remove the housing cover and unscrew the starter screws. Remove the item. Then they remove the flywheel by unscrewing the nut that holds it, unscrew the flywheel nut. You need to twist to the left. Remove the flywheel. Then dismantle the clutch, oil pump drive and carburetor.
After that, the motor is removed and disassembled. It is held by 4 screws on the bottom of the saw. You need to untwist them and remove the motor. Then the engine itself is disassembled. Unscrew the crankcase screws, remove it. Then dismantle the crankshaft, oil seals, bearings and piston rings. At the end of disassembly, repairs and troubleshooting are performed.
After repair, the tool will need to be reassembled. To do this, install the piston on the connecting rod. The arrow on it should look along the chain, and to the left of the piston there will be the side of the crankshaft in which you want to mount the flywheel. They put the piston in the cylinder. Install the bearings, seals and circlip into the cylinder. After that, degrease the place of fixing the crankcase and install it in its place. When reassembling, follow the reverse sequence for dismantling.
How to remove and replace an asterisk
Replacing the sprocket on a chainsaw is needed in cases when:
- Jams the movement of the chain;
- The drive sprocket has worn out.
To replace it, you need to remove the chain saw sprocket. The sprocket teeth must not deviate from the required dimensions, otherwise the saw operation will be accompanied by vibration, which will lead to damage to the crankshaft and bearings. The lifespan of the sprocket is 2 times that of the chain. Use 2-3 chains until the cutting surface is abraded. After that, change the asterisk. It is located behind the clutch. Remove the clutch cover.
Remove the bar, chain, and clutch. But first you need to fix the crankshaft. Then the stripper is placed in the hole of the sleeve and turned clockwise. Remove the clutch. There is an asterisk behind it. Now it is being dismantled. If it is defective, it is replaced.
Fills the candle
If you notice that you are pouring a candle on a Stihl chainsaw, then a malfunction may have occurred in the fuel system. The engine must run on a mixture of gasoline and oil. If the mixture is lean, the power is reduced, the cylinder overheats and the saw systems wear out. A wet plug on a Stihl chainsaw is due to a disproportionate fuel mixture. Lack of air in the mixture prevents the emulsion from burning properly.
Spark plug oiling also causes the use of oil for 4-stroke engines, piston wear. If such a malfunction occurs, it is necessary to remove the gas tank cap and adjust the fuel supply. The air intake should be repaired. The clogged filter must be blown out with air, or it is better to replace it. How you can clean the filters is described in the instruction manual for the chainsaw.
It will be possible to determine the quality of the mixture using a spark plug insulator. If a brown color appears on it, it means that the quality of the mixture is normal. White color or soot indicates a poor or over-enriched composition of the mixture.
The candle is the cause of oiling. Interruptions in spark formation are observed when the gap is incorrectly set. In the instructions for the repair and operation of the device, the distance between the contacts of the candle is given. If you do not have such data, then you can set 0.7-1 mm.
If the gap is less, then the efficiency of ignition of the mixture decreases, if it is larger, then interruptions in the formation of a spark occur. To eliminate the over-enrichment of the mixture, the motor is purged. In this case, it is necessary to remove the candle and turn the crankshaft several times with a manual starter.
How to assemble a new lawn mower starter?
For starter assembly do the following manipulations.
- Pass one end of the string through the opening at the beginning of the spool and tie it in a knot. The knot must not pass through the hole. Otherwise, you will disassemble the starter again.
- Wind the cord around the spool itself.
- Install the spring into the starter housing, hook one end of it in the groove and wind it. For convenient winding, twist the body counterclockwise.
- Place the ratchet on the spring.
- Hook the return spring to the ratchet itself, secure it to the spool.
- Install the main spring and housing with the assembled ratchet, connect the starter parts together and tighten with the main bolt.
After assembling the starter, pass the free end of the cord through the hole in the housing for the reel. Re-pass the same end through the hole in the handle that the cord is pulling on. Tie a strong knot on the handle. Check the operation of the starter handbrake.
How tight is the spring cocking?
It is possible to give the spring the necessary potential force required for a clear and fast winding of the cord, by determining the length of the cord in turns. To prevent the cord handle from drooping, add 1-2 more turns to the number of turns. So, if the cord has a length of 5 turns of the coil, then, when charging the spring, turn the coil 6-7 full turns.
Worst failure scenario
There are times when the starter is still operational, but a worn out cord can break, for example. The ratchet has not yet had time to work when the engine is started, and the remnants of the cord are immediately wound on the coil, the return spring loses its hooks, the grooves in the starter housing break. The result is the replacement of both the springs and the housing.