Don't be, it's not that complicated.
Jet numbers are a rating for the # of cc's of gasoline that flow through the jet in one minute, from a height of 50 centimeters (for Mikuni). Dyno-jets are measured in millimeters (so a DJ150 is 1.5mm).
Winter air is colder and thus more dense, so you need more fuel to maintain an ideal ratio than you do in summer when it's less dense, so winter jets are fatter.
38mm refers to the bore diameter of a carb, roundslides are a type of carburetor with, well, a round slide throttle (as opposed to flat-slides)
Piston wash refers to what the face of the piston looks like, and reading the "washed" i.e non-charred areas. Too much charring means too lean, too much "wash" means too rich. It's more of a 2 stroke thing since most of the char is deposits from the oil being burned.
It's something snowmobilers use as an excuse for losing races, blowing up engines,
2s engine failure has few causes. All but 1 come back to user interface..lean wash is an after failure diag. Not possible to be an " excuse " as its a direct result or "effect" of lean jetting. Jetting can be an excuse.
or spending time in the garage away from a nagging wife.
lmao amen to that