@hans:
That more stable running probably was due to the more recessed location of the choke valve.

@dar/wasp
in my 50cc racer, we found a best total intake duct length (by cut 'n try) of 40cm, with the carb located 1/3rd that distance from the piston skirt.
Torque started above 9000 rpm. Anything below that rpm caused the engine to flood instantly if the throttle was more than just slightly open, due to the multiple blowback gas passage past the jets.