Buying a used carburetor is always a gamble. If you are buying sight unseen then don't pay more than junk price for it without first getting a gaurantee and checking their feedback. Don't deal with anyone with a lot of bad feedback. Don't even give them the chance to lie to you.
I have 114 positive and one negative from a guy who didn't pay for his purchase. I don't think that's very important. As long as everyone else was happy.

AL