Not symptoms of a worn piston/sleeve but a way to check it out and know for sure.
Dissassemble the engine including removing the piston and sleeve.
Slide the piston up into sleeve untill it stops.
If it stops approxamatly 1/8" from the top of the sleeve then you have a good set.
The farther into the sleeve the piston goes the more worn the set is.
If the piston goes to the top of the sleeve, or farther, it is well past it's useable life.
There are some that claim that sleeves can be "repinched" and there are DIY ways as well as companies who will do the pinching for you. I have tried the DIY stuff and had very poor luck with it. I have not tried any of the repinching services but others claim to have good results. Personally, I'll just get new parts and be sure.