Hallo guys!
Why are you bothering!!!! The Webra engines and their carbs are one of the markets best ...! They work in th esame manner that all others do...by setting the highspeed needle first then....setting the lowspeed needle!!!
The idle needle is regulatin fuel....all fuel if screwd all in ,but that you should not do!
The highspeed needle is also regulatin fuel...all fuel if screwed in!!
The secret to good engine behaviour is to open the idle needle enough,(what that is).
On the Webra .40 -. 50 that means that the idle needle should be approximately 1mm from the orrifice at full throttle opening.
This is the basic set-up!
Then full power is set with the highspeed needle. Highspeed needle regulates the main distribution of fuel to the engine, the idle needle just restricts the fuel getting in the carb at midrange and idle.
Its that easy!

Regards!
Jan K
Sweden