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I own Husqvarna 357 and I am confused. If a saw has poor compression, could replacing the rings only and give it a boost? Or is it usually in need of more work such as replacing the cylinder and piston meanwhile? When do you know if you just need a new cylinder/piston/rings for your saw? I see most of stores in the marketplace sell piston cylinder and piston rings as a set and seldom have piston rings or cylinder separately. I would like to get a good base reference when I need replacements. Thank you.

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    Since most chainsaws are 2-stroke, I'd suggest the first place to look for loss of compression in the engine is the one-way reed valve which seals the cylinder during the compression portion of the cycle. This would be a first look before even considering the piston/rings/cylinder. Apr 4 '18 at 11:32
  • Make sure you have the choke fully open as well as the throttle when performing a compression test.
    – user288719
    Dec 13 '19 at 2:55
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Normally with those chainsaw motors the problem is wear on the cylinder. If it where a car, you´d do a new honing of the cylinders and put in oversize pistons. Given the prices of chainsaw spare parts this is not economical, so you just replace the whole set.

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It's possible for the rings to wear and loose tension, with the piston and bore showing little sign of wear.In that case putting in new rings will probably revitalise the engine.Symptoms of that would be low compression,lack of power,but the saw still running and the piston / bore being on good condition. But more common,or at least total failures,usually involve damage to at least the piston, and often the bore An air leak or carb fault makes the saw run lean, it overheats, and the piston starts to physically melt. At that point it's toast, and maybe the cylinder too. Another failure is foreign matter, dust etc getting past the air cleaner, and that's going to physically wear (score) the piston, again probably beyond what new rings can mask. But I guess the real answer if what the internals look like once you have the engine apart. Then you can see what physical damage there is. If the piston and bore are good, then rings is probably all it needs. More damage or wear? Replace what you need to.

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Some people don't know which part was bad,so they prefer to buy a whole chainsaw parts,after all,a whole set including Cylinder,piston and rings are not expensive.I see,Cylinder Piston Rings Kit online For Husqvarna 357 at enter link description here is about $22.50-a price to please almost every pocketbook.Not sure the longevity.

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Over time, chainsaw cylinder start to wear just like any other thing on the earth. I suggest you test your compression first. if it is poor, disassemble the saw and take a look at the cylinder and piston. If they seem to be worn, you need to replace them.

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    What does this add to the existing answers?
    – Solar Mike
    Oct 16 '19 at 6:55
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In daily life,there are bits of dust, flakes of carbon etc that are bigger than the oil film. So the engine gradually wears out over time. The rings are the "pressure point", so they do tend to rear first. The metal of the rings can also loose their "spring" over time, so they don't press on the cylinder walls and seal properly. So this some case only the rings need replacing. Other times, the engines "cooked" or eaten a handful of grit, there is more damage and need to replace the whole set(cylinder,piston as well as piston rings).

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