I've got two bikes here, both 1977 models. One is a 50V and the other a 40TL. Both have the larger style gurtner carb.
The carb on the 50V has a 6mm stud to attach the air filter, and a choke cable than enters from the bottom.
The carb on the 40TL has a 5mm stud, and the choke cable enters from the top, next to the throttle.
There are a couple other minor differences, like the design of the mounting clamp. Other than the obvious differences, are there any actual functional differences between the two carbs? Can they be interchanged? What's the point of the variations?