I got this saw from my friend it was working good till the piston got scratched in the cylinder the piston ring was hard to pull off (from muffler side) the cylinder was scratched too. The fuel was ok but I don't know what is the main problem with it. Please to give me what is the reason that After it I cleaned the piston I got the new ring i did a cylinder hoen and situation was repeated Thank You Verry much Wojtek