Thanks for the info, EK. So I take it then that the carb with the 5mm stud is for a 20mph model?
In my brief experience with them, the gurtner has not overly impressed me. I have seen much worse, though.. like the Amal concentric. All I can say is "Lowest bidder". And then there is the Amal monobloc - what were they thinking with that float bowl cover?
Thing is, I'm one of those folks who either keeps it as completely original as possible, or just modifies at will. I'd like to be able to make the gurtners work.
If I had to modify it, I'd probably go for a dellorto. I'm quite fond of those carbs.