P/N 631021A is the needle and seat plus bowl gasket and bowl nut gasket, the seat is not available as a separate item.Waddja do, pick the little rascal out then drop it?
Install it with a little lubricant, light oil or WD-40 work well,and push in straight with a pin punch, groove side down.

Thankyou, Canguy. I am going to tear down the carb to clean it. I was just doing some preparation in case I have to deal with a parts guy. Since my lawn mower guy retired to FL, I need numbers to get parts.

I took the bowl and the mainjet off. There was some black, sediment in the bowl and a big chunk of something sitting in the top of the main jet. I drained the tank into a glass jar and it was clean. That pretty much leaves the 30 yr fuel hose as a suspect. Anyway,I got it and its little brother running good, and waiting for the snow in the tool shed. I also dosed the mowers with Stabil and MMO