RTang, they are one and the same.

When the mixture is set too lean, the engine still gets sufficient lubrication.

The leaner fuel mixture ignites sooner and burns more quickly. As a result, the maximum pressure is reached before the piston reaches TDC and as a consequential result, more heat is absorbed by the piston (faster) and cylinder, the piston expands more and contacts the sleeve. The engine heats up still more.

If you are lucky, the engine will stop immediately, if not, this could be the end of its life.


When the engine gets insufficient cooling, the ignition and burn processes also happen faster, like with too lean a mixture...

Both could have the same result.


The most profound effect of the needle is not on fuel consumption, but on ignition timing.


ABC engines can survive a lean-run.

A ringed engine will most likely need a re-ring, if a lean run is prolonged.


I had an FP that did the same; leaned-out and quit after a few minutes.
It stopped doing it and began to behave normally, after the sleeve's nickel coating pealed partially...