Put enough hours on a 2159 to wear out the piston skirts- and the plastic clamp will fail, they just age and the plastic does become brittle. At that kind of use age, the AV are probably not doing their best and the hinging of tank to crankcase does not help the matter.
I believe being a green fuel cap saw, it should have the metal band clamp? The cat can be removed from the muffler, but requires some chopping and gluing.
If you swap out the muffler, the saw will need retuning to suit the modification- but if you play around with base gaskets and timing, you will be doing that anyhow- or a nice 2159 will go down in value very quickly.
In my opinion, these are THE best 60cc range saw of the era and will bat way above their designated spot in the line up. Getting harder to find K095 24" bars, but in softwood, these saws will pull one with standard 3/8 chain, even easier with skip sequence, they are perhaps happiest with a bar and sharp chain in the 18-20 inch 3/8 range.