Here's some photos of variants in the 40mm carb. These come from here
. Ironically it was Igormortis who made me aware of this site when I was having jetting issues & was considering using an air fuel meter.
Bing - 123, no idea where the breather vent is, sorry. Might still be the bottom of the float bowl?
Bing - 123a, vent is just below the plastic bing cover
Bing - 123a2. Breather port is the big cap above the riveted bing plate, & near the inlet. Looks like it would be relatively easy to take the cap off, & put a breather tube on that, or to create a spigot to take the breather much higher on the bike.