Need carb help and part ID

Hello, I just bought a kz440 with a bad carb diaphragm. I .
took the carb apart to clean it and install new diaphragms. I cleaned out everything with carb cleaner and blew it out with compressed air. When I was done I noticed a very small brass part left on the work bench. It is pointed on one end and flat on the other, hollow with a very small hole running through it. I went ahead and installed the carb anyway just to see what it would do. It will run with the choke fully closed, but as soon as you open the choke it will run wide open for a second and shut off. If anyone has any ideas it would be greatly appreciated.

thanks

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Not knowing your particular carburetor, I would guess that part restricts a air/vacuum passage. Sounds like your engine is running extremely lean now.