I don't imagine this is what you want, but...
I have a 257 which is missing a number of big and small parts; including top cover, muffler, and clutch cover assemblies.
It has a HDA120 carb. I have no history with the saw...including the carb.
I want to sell the whole thing for $45 plus actual retail USPS shipping. If you are at all interested, I can post the inventory of missing parts and pics.