Hello Pepin, any positive happens since yesterday? The "Leerlaufluftschraube" = the small screw; the "Leerlaufschraube" is the Big one. U screw the Big one in to have a stable RPM (for example, 2000RPM); after that u adjust the small "Leerlaufluftschraube" to find the highest available RPM, its like a
Gauss-curve. After then u screw the Big "Leerlaufschraube" back to reduce the RPM to example 1500 and try to find the highest RPM with the small screw on that Adjustment again. The fine tuning cause the wrong exhaust u can adjust AFTER your Carburetor works fine - in idle and the moment between idle and throttle.
U have mounted the Parts of the Carburetor Piston correctly? Piston -> Clamp with Needle -> Plastic Part -> Spring...?
U have mounted the Small Steel Wire in the Throttle / steering Handlebar correctly? There is a wrong position available to have a quarter Circle to throttle.
Big Screw = Leerlaufschraube = directly adjust the RPM in idle with the Position of the Piston; screw in = higher RPM
small screw = Leerlaufluftschraube = adjust the RPM indirectly by balancing air and fuel in idle. Screw in = lower air, fat run; screw out = Lower fuel = higher RPM, but lower performance in the moment you open the throttle.
Robert