Thanks Carbking!
It is possible that the number is 2101S. The "YF210" is very legible. The last digit, either a "0" or "1" is very faint, not stamped very deep. The "S" is below the rest of the stamp by a half line. So, who knows? :confused:
I put the carb on today and it made all the difference in the world. No more "rottenchestor rot-pots" for me!

I think I'll still put a kit in it. Do the 2100S and the 2101S take the same kit?
Thanks,
Steve