https://www.mopedarmy.com/wiki/Sachs_505/1a_performance
you B will have all the same performance considerations as the A.
Once you've replaced cylinder carb and pipe, it's essentially identical to the A.
The D has a longer stroke and results in more torque and more power, you can get this also by using the long stroke aftermarket crank or a used D crank, but the gain's probably not worth it for you - just carb pipe and cylinder is good to go
Word of caution though, the intake on the airsal really only fits the stock carb well, if you do intend to use the square bing, at least upgrade to the 12mm from the A or D engines, your B carb is 10mm and suuuuuuuckkkkkkksssss
basically the intake with the kit is shit. but a new intake is another 50+ bucks. Still, best setup would be like a VM16 or 18 or even a 15 SHA.
you can modify a stock intake to work, but not your stock B intake, gotta be from an A.
I know this is confusing, if you want an easy bolt-on setup, MLM 15 SHA intake, 15mm genuine dellorto (or arbeo) SHA, 28mm header and clamp-on exhaust, and the airsal 70. like $400 bucks (see attachment)
alternately use the included airsal intake and either find a used 12mm SACHS square bing (I can send you one but you'll have to swap some parts from yours - just use the 12mm bored body). treats is out of stock: https://www.treatland.tv/sachs-12mm-bing-CLONE-carburetor-p/sachs-12mm-bing-square.htm
be aware the standard bing carbs like from puchs do NOT fit. they fit the intake but dont have clearance and hit the frame and hte engine so it cant work without weird spacers and shit
