Just seeking some clarification.
As I understand it weakness can cause surging / bucking on a 2 stroke.
On the DT carb, my understanding is that turning the airscrew IN makes the idle / low speed mixture RICHER
Assuming I have the above right, why does mine run better with the air screw slightly further out - WEAKER than stock?
Did a little more "fiine tuning" on mine yesterday and found that with the screw slightly further out (1.75 turns) it runs a lot better than the stock position of 1.5 turns.
Everything is stock apart from a Rex Speedshop conversion.

These settings from the factory are close… so many different things can/will affect performance.
Sneezles61

I have always thought of factory settings as a "baseliine" - totally agree about other factors influencing the settings.

Also the fuel we get these days is different from when these bikes were first made.

As you say , fuel today is quite different to when the bike was new .
Your new setting is still within working range for your existing pilot jet , so no alterations necessary there .
The engine tells you how much fuel it wants , and optimal setting may vary a bit from OEM spec .

If you're talking bucking slowing down on a closed throttle like the pre "74 360's do then a mate leaned out his RT2 with a lot smaller pilot jet & pretty much cure it but i thought he was pushing his luck slowing down from highway speed but got away with it. Was a borderline too lean idle though & probably took time to settle on a cold morning start.
If you mean bucking just cruising along at medium revs the maybe raising the clip could help a bit. Might even find the needle & jet are worn enough to upset it.

my carb has stock jets and needle in stock position. To eradicate my surging/bucking and over run, I had to have the low speed screw at 3/4 turn out then re set the tick over screw, this worked for me.
blubbery when cold but warm perfect through out the rev range and no surging/bucking and over run notable.

for what it is worth I reduced the bucking on my DT360 - which i would characterize as up and down surging at a very light load - by upping the pilot jet by one size.  Air screw had to come out a bit more than 1.5 turns to add a bit more air, but it helped greatly and because I went richer vs. leaner I don't have to worry about toasting engine.  

While I don't think it has anything to do with aforementioned condition, I also upped the main one size (190 if I remember correctly) and raised the needle a slot richer too if I recall so its a bit richer on longer hi speed runs (e.g. 55mpg ish)  runs down the road to trail head.  

Plug is a nice dark brown and with semi-synthetic lucas oil I have 2500 miles on same plug I put in after melting piston 2 years ago

I did a thorough cleaning of my DT360 carb and found that that air jet had a lot of crud in it.  I used a number drill and gently cleared it.  I also cleaned the needle jet area where it meets up with the air jet. Unfortunately, i have not had a chance to ride it yet to see if helped with the surging but it makes sense to me that this crud would have an effect in the transition between the pilot system and the main system.  I’m curious to hear what others think.  It will be a while before I get this bike running again.