Another scenario that sets up a too rich condition is on the rare occasion that we over fill the tank and the muffler fills up with fuel, that almost guarantees a backwards start with the engine running backwards for a few scary seconds.
(quote) I always suggest to guys not familiar to 4-stroke cycle engines to open the main needle a half turn or more on a new to them engine before starting the engine to ensure its rich to begin with. (quote)
Sorta like always tuning a guitar from flat upward, never from sharp downward.