A misfire scenario in a two-stroke engine where the air-fuel mixture fails to ignite during a cycle, causing the engine to fire only once every four strokes instead of every two. This typically happens under light loads or rich fuel conditions when exhaust gases fail to clear the cylinder, diluting the fresh intake charge until a second cycle pumps enough fresh mixture in to achieve combustion.
Heard on the job
The dirt bike is four-stroking badly at idle, so we need to lean out the pilot jet a bit.
Insider tip
If a two-stroke engine is four-stroking at wide-open throttle, the main jet is almost certainly too rich.