Got a 73 at3 Looking for the right part # for the float chamber gasket ordered the 156-14184-00-00 that's in both AT parts lists but it is the wrong gasket carb is a mikuni 316e3

Thanks!

Not sure what "parts list" you're using...  AT2 and AT3 take a different gasket with a 304 prefix.  #11 here:  www.partzilla.com/catalog/yamaha/motorcycle/1973/at3/carburetor

Its that at1-c /at1mx catalog is there an at3 catalog hiding on here somewhere?

Yes, some parts changed over the years so you generally need to use the list for your model. Anyway, I gave you a link to one of thousands of online parts books...  those are usually the most up to date.  CMSNL is another good source as they sometimes have new parts others don't..

There is a AT2/AT3/CT2/CT3 list in the back of the "71-73 Combined Yamaha Service Manual with Parts Catalogue" (emphasis added) in the Tech Library here. 

The problem with the printed list in that manual and the online lists is the lists were originally shared among the AT and CT and a lot of the original information as to which part fits which model (AT or CT) got lost in the translation...  Sometimes you need to use common sense and detective work (Hint: the model code prefix is important) to find the right parts.  For example, an AT and a CT use different pistons since the CT has a much bigger bore.  So you have to pay attention to the part number prefix (first 3 numbers) to get the right one.  You can always ask questions here too.

You can get the gaskets from Sudco.