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.
Rapid Racing Inc.
"When in doubt Gas it, It won't help but it ends the suspense."