Originally Posted by BarelyAWake
I agree w/ya Davezilla. Insofar as winter rejetting & plug range swapouts... well... the American south west gets chilly n'all & folks can ofc do whatever they wish in the quest for HP - but I gotta mention it does get a bit cool up here too from time to time. The winter & summer extremes in Maine are no more then between -20°F & 100°F usually & granted, that t'aint near as much as some places but to my knowledge no one around these parts mucks about with plug ranges & rejetting in their 'smokers two or four due to the temperature change (including dirtbikes, quads, chainsaws & other year-round uses).
Yea, air density does have an effect & it can even be pronounced enough to "feel" a difference on a cool day with our engines - but consider for a moment small aircraft which routinely experience extreme variations in air density and temperature as they change altitude. At a set RPM in combination with both the EGT and CHT readings (exhaust & head temps) a manual mix control is utilized to maintain the proper fuel/air ratio as they ascend or descend... but no one worries the heat range of their plugs as they do so. This includes the not "computer-controlled" ultralight & sport/experimental classes which often fly two strokes as well as the fours, as I did with a Rotax 440 (two stroke) in a Quicksilver MX (in both winter & summer BTW, same range plugs).
So... you can "sweat" such details if ya wanna but honestly you'll be just fine picking a range/ratio that seems good for the engine & sticking with it no matter the season *shrug*
My point exactly... it don't matter if it's a big 18 wheeler or a sub compact, motorcycle or chainsaw, liquid cooled, or air cooled, 2 stroke or 4 stroke, there's no reason to sweat over what plugs you got installed or what jets you got installed, once the engine is tuned it'll run in all 4 seasons.