I have a 1946 2 ton with a W - 1 Carter. Looked to be the original carb.
When I went to buy a rebuild kit they needed to see the carb to know if it was a YF or not.
The way they told me was that if the accelerator pump rod was round or flat.
My carb's rod was flat. Though I am not sure if that meant if it was a YF or not at this point.
If the tag is missing on a Carter W-1, a knowedgable technician can still identify the carburetor at least far enough to determine the proper kit. The first question is to determine if the pump shaft is round or flat. Carter used round pump shafts from 1932 to 1940, and flat pump shafts from 1941 to 1949.
Depending on the answer, there are two different sets of questions to go from there.
Tim - I forgot about the 616s (fleet carb) when I made my earlier post. They are quite scarce, but not as scarce as someone that actually wants one. I didn't forget the 517s, but since the OP had a YF (downdraft carb), I omitted the 517s (updraft carb).
If anyone is interested in the set of questions, it is pretty easy to figure out from this link:
http://www.thecarburetorshop.com/CarterChevroletW1.htmJon.
