I have never seen this before...

[rkshed]

Yesterday, I tore down 2 fairly new Poulin Pros (Lowe's version) because they were both light on compression. 1 had 100 psi and 1 had 125 psi. They both just quit running after around 15-20 hrs of use. Yup, used good premix, air filter clean and correct plug. Both cylinders scored beyond use. Apparently there is an inherant problem with these Poulins that allows debris in or something.
Anyhow, when I popped the cylinder off one, out dropped 2 pcs of plastic?? Figured out they slip into the liner and appear to be for the transfer ports. Maybe adjustable?
I have raced and ridden off road 2-strokes for over 35 years and have NEVER seen plastic used as part of a liner.
Is this common in chainsaws for some reason? I can't imagine that it would offer long life. The two pcs were scored as badly as the rest of the cylinder. Did the piston skirt cut the plastic which caused all the scoring?
What have you all seen?

 

[rwhite]

It's not off a plastic reed block is it? That seems the most likely spot for it to come from unless a piece of air filter came off. The plastic probably didn't cause the scoring in the sense that it is softer than the liner. What it did probably do was get wedged or melted on one side of the piston and not allow the rings the float which may have resulted in the rings pushing against the cylinder wall and scoring them. Another possiblity is the the reed block came apart and it ran lean and got real hot.

 

[rkshed]

The plastic is part of the cylinder. Its on both sides, approximately 1 inch wide by 3 inches long and it sits just below the rings on the intake stroke. The piston skirt uses it as part of the cylinder. Weird.
Turns out the ring didn't stick either. No seizing. Just grooves like it ate sand!