at which rpm needle jet begin to raise? what are signs of clogged bypass holes?

I read a lot of informations on how the bing 64 works in general terms and details.

But i have never understood whether from idle to 3000 rpm (where there are always more or less marked roughnesses in rotax 912 engines) only the idle jet and the bypass holes are involved or if at these rpm the needle jet has already started to lift.

Many  912's are rought from 2000 to 3000. I suspect that  in addtion of dirty idle jets, clogged bypass holes are the cause and a lot of people do not even know their existence!

In your experience what are the signs of clogged bypass holes?

thanks