What are do all the different jets control? Whats does the actually size mean not like one is bigger but what does the 240 or whatever mean for the main jet? Also what are the differences of 4 and 2 stroke carbs if there are any? Also what size increments do the main jets come in?

 

Most 2 and 4 stroke carbs are different but some types can be used on both, like Lectron power jet carbs.

Most carbs use main and pilot jets along with a needle, air screw, idle adjustment, and choke.
Comparing Mikuni and Keihin, the jets are a little different.

Main jets affect the 3/4 to wide open throttle circuit. Keihin main jets go up in 2 or 3 # increments like 160, 162, 165, 168, 170, 172.....
Mikuni main jets are numbered like 210, 220, 230, 240.....

Needles come in different sizes also. The needle setting controls the circuit between idle and wide open, mostly a mid range. The lengths, diameters, and tapers are all represented by letters and/or numbers. A needle can be adjusted by raising it or lowering in on the carbs slide.

The pilot jet affects the idle circuit to about 1/4 to mid throttle. A Keihin size example is #45, 48, 50.....

The air screw basically fine tunes the pilot circuit for adjusting idle, or just over idle, by allowing more or less air in. If you have to turn the screw in all the way to make it run good, it means you need a larger pilot and if you have to turn the screw out, you need a smaller pilot. An ideal setting would be 1-2 turns out.

Most differences between 2 and 4 stroke carbs are how they let air through. 2 stroke carbs raise a slide(round, oval, flat, and "D" slides are the most common)and 4 stroke carbs open a butterfly valve but there are some exceptions.
ERIC