I messed around with a saw all summer with similar problems. Started checking & replacing plug, fuel lines, filter, intake gasket, carb kits, then a $40 carb, Finally, I got it fixed when I spent another $120 getting the jug and piston replaced.
I should of spent $40 right off the bat on a compression tester that would of told me right away.
I wonder if my problems started with a bad carb pump or leak ( too lean), but during the time I was messing around with everything did I burn the piston up? Without the tester I'll never know where I was starting from. The Husky 55 is 19 years old so I don't feel too bad spending a little money.