My mistake! Its a WYJ carb.
The exact stock carb on the Fuji BF25/34 Engine is a Walbro WT690 and I believe it is an 11.1 mm venturi. RCIGN1 may correct me if I am wrong.[:-]
However I retract my statement about it being the same carb as the Zenoah G26. It is not the same carb but is very similar.