if that’s all it is, that’s great. Can’t see how an engine with a single piston ring wouldn’t leak and still run. Yes, we’ve melted a couple pistons so well into the bore that they probably had zero leak down.
Actually I think they are looking for air leaks. On engines with restricted carburetion example Yamaha Jr, Sportsman with the WB55 carb and also with Comer K-80s some builder have intentionally leaked air to the engine via intake manifold or crank seals. More air=more fuel+more power. They can be a bitch to start though.
Ever notice the smell of starter fluid on the grids has become stronger and stronger over the yrs. This is the leading cause of the source. Not the only reason mind you, but…