I removed the muffler and when looking at the side of the piston in the exhause port I see two small groves in the piston, maybe from dirt or debris, but perhaps metal from something. When turning the prop it is clear that air is escaping past the cylinder and bubbles of oil or fuel are seen in the port. I imagine that the piston and sleeve are scored enough to leak on compression. Will replacing the two items correct the problem? Placing heavy oil on the piston will temporarily increase felt compression which tends to confirm the cause.