For those running the stock BST carburetor (no jetting or needle changes, no holes drilled) here is a pic of needle wear after 52,000 miles (83,000 Km).
Just a tiny bit of 'stepping'. (not a great pic but if you enlarge it on your screen you can see it a little better.)
I replaced it and the diaphragm anyway with parts from an almost new carb that I bought here for a nice price.
........shu