CV Carb Part Question

I know that this is not a Gold Wing question but many of us have bikes with CV carbs . I have a 72 CB350 that I decided to clean the carburetors on (Keihin 722A) and found that there is a piece missing under the lid of one of the carbs. Here are a couple of pictures.

Here is the piece:



It goes on the underside of the lid as you can see in the middle of the lid:



If I can't find it, and I am pretty sure that it was missing while it was running, is it critical?

I’m thinking it’s like a cushion for the slide to hit when it suck up all the way to the top by vacuum ..seems like you could make something to do the same thing or get one somewhere

I think your right Joe . . I have rebuilt several sets of CV's years ago , the spring fits around that place in the top , but I never had to hunt any piece like that. :laptop: