I have a Yamaha XS750 1979 rebuilt as a cafe racer (not by me). I need to buy some parts for the carb, but cant seem to find out what carb I have - no ID number anywhere. I think the original is called BS34 but not sure.
Can anyone help me please ?
Not sure about the model number, but the parts diagram for the original looks like what your photos show.
http://www.partzilla.com/parts/search/Yamaha/Motorcycle/1979/XS750F/CARBURETOR/parts.html
I believe they are a BS38 Constant Velocity (CV) Mikuni Carb. Look at the center pair of images, which are a dual setup, but appears to be the same. According to this they were used from 1976-1979, which fits your description.